feat: add MCP server support with global library and per-project toggles

Add Model Context Protocol (MCP) server configuration support. Users can
define MCP servers globally (new sidebar tab) and enable them per-project.
Enabled servers are injected into containers as MCP_SERVERS_JSON env var
and merged into ~/.claude.json by the entrypoint.

Backend: McpServer model, McpStore (JSON + atomic writes), 4 CRUD commands,
container injection with fingerprint-based recreation detection.
Frontend: MCP sidebar tab, McpPanel/McpServerCard components, useMcpServers
hook, per-project MCP checkboxes in ProjectCard config.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src/components/mcp/McpPanel.tsx

@@ -0,0 +1,76 @@
+import { useState, useEffect } from "react";
+import { useMcpServers } from "../../hooks/useMcpServers";
+import McpServerCard from "./McpServerCard";
+
+export default function McpPanel() {
+  const { mcpServers, refresh, add, update, remove } = useMcpServers();
+  const [newName, setNewName] = useState("");
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    refresh();
+  }, []); // eslint-disable-line react-hooks/exhaustive-deps
+
+  const handleAdd = async () => {
+    const name = newName.trim();
+    if (!name) return;
+    setError(null);
+    try {
+      await add(name);
+      setNewName("");
+    } catch (e) {
+      setError(String(e));
+    }
+  };
+
+  return (
+    <div className="space-y-3 p-2">
+      <div>
+        <h2 className="text-sm font-semibold text-[var(--text-primary)]">MCP Servers</h2>
+        <p className="text-xs text-[var(--text-secondary)] mt-0.5">
+          Define MCP servers globally, then enable them per-project.
+        </p>
+      </div>
+
+      {/* Add new server */}
+      <div className="flex gap-1">
+        <input
+          value={newName}
+          onChange={(e) => setNewName(e.target.value)}
+          onKeyDown={(e) => { if (e.key === "Enter") handleAdd(); }}
+          placeholder="Server name..."
+          className="flex-1 px-2 py-1 bg-[var(--bg-primary)] border border-[var(--border-color)] rounded text-xs text-[var(--text-primary)] focus:outline-none focus:border-[var(--accent)]"
+        />
+        <button
+          onClick={handleAdd}
+          disabled={!newName.trim()}
+          className="px-3 py-1 text-xs bg-[var(--accent)] text-white rounded hover:bg-[var(--accent-hover)] disabled:opacity-50 transition-colors"
+        >
+          Add
+        </button>
+      </div>
+
+      {error && (
+        <div className="text-xs text-[var(--error)]">{error}</div>
+      )}
+
+      {/* Server list */}
+      <div className="space-y-2">
+        {mcpServers.length === 0 ? (
+          <p className="text-xs text-[var(--text-secondary)] italic">
+            No MCP servers configured.
+          </p>
+        ) : (
+          mcpServers.map((server) => (
+            <McpServerCard
+              key={server.id}
+              server={server}
+              onUpdate={update}
+              onRemove={remove}
+            />
+          ))
+        )}
+      </div>
+    </div>
+  );
+}

app/src/components/mcp/McpServerCard.tsx

@@ -0,0 +1,262 @@
+import { useState, useEffect } from "react";
+import type { McpServer, McpTransportType } from "../../lib/types";
+
+interface Props {
+  server: McpServer;
+  onUpdate: (server: McpServer) => Promise<McpServer | void>;
+  onRemove: (id: string) => Promise<void>;
+}
+
+export default function McpServerCard({ server, onUpdate, onRemove }: Props) {
+  const [expanded, setExpanded] = useState(false);
+  const [name, setName] = useState(server.name);
+  const [transportType, setTransportType] = useState<McpTransportType>(server.transport_type);
+  const [command, setCommand] = useState(server.command ?? "");
+  const [args, setArgs] = useState(server.args.join(" "));
+  const [envPairs, setEnvPairs] = useState<[string, string][]>(Object.entries(server.env));
+  const [url, setUrl] = useState(server.url ?? "");
+  const [headerPairs, setHeaderPairs] = useState<[string, string][]>(Object.entries(server.headers));
+
+  useEffect(() => {
+    setName(server.name);
+    setTransportType(server.transport_type);
+    setCommand(server.command ?? "");
+    setArgs(server.args.join(" "));
+    setEnvPairs(Object.entries(server.env));
+    setUrl(server.url ?? "");
+    setHeaderPairs(Object.entries(server.headers));
+  }, [server]);
+
+  const saveServer = async (patch: Partial<McpServer>) => {
+    try {
+      await onUpdate({ ...server, ...patch });
+    } catch (err) {
+      console.error("Failed to update MCP server:", err);
+    }
+  };
+
+  const handleNameBlur = () => {
+    if (name !== server.name) saveServer({ name });
+  };
+
+  const handleTransportChange = (t: McpTransportType) => {
+    setTransportType(t);
+    saveServer({ transport_type: t });
+  };
+
+  const handleCommandBlur = () => {
+    saveServer({ command: command || null });
+  };
+
+  const handleArgsBlur = () => {
+    const parsed = args.trim() ? args.trim().split(/\s+/) : [];
+    saveServer({ args: parsed });
+  };
+
+  const handleUrlBlur = () => {
+    saveServer({ url: url || null });
+  };
+
+  const saveEnv = (pairs: [string, string][]) => {
+    const env: Record<string, string> = {};
+    for (const [k, v] of pairs) {
+      if (k.trim()) env[k.trim()] = v;
+    }
+    saveServer({ env });
+  };
+
+  const saveHeaders = (pairs: [string, string][]) => {
+    const headers: Record<string, string> = {};
+    for (const [k, v] of pairs) {
+      if (k.trim()) headers[k.trim()] = v;
+    }
+    saveServer({ headers });
+  };
+
+  const inputCls = "w-full px-2 py-1 bg-[var(--bg-primary)] border border-[var(--border-color)] rounded text-xs text-[var(--text-primary)] focus:outline-none focus:border-[var(--accent)]";
+
+  const transportBadge = {
+    stdio: "Stdio",
+    http: "HTTP",
+    sse: "SSE",
+  }[transportType];
+
+  return (
+    <div className="border border-[var(--border-color)] rounded bg-[var(--bg-primary)]">
+      {/* Header */}
+      <div className="flex items-center gap-2 px-3 py-2">
+        <button
+          onClick={() => setExpanded(!expanded)}
+          className="flex-1 flex items-center gap-2 text-left min-w-0"
+        >
+          <span className="text-xs text-[var(--text-secondary)]">{expanded ? "\u25BC" : "\u25B6"}</span>
+          <span className="text-sm font-medium truncate">{server.name}</span>
+          <span className="text-xs px-1.5 py-0.5 rounded bg-[var(--bg-secondary)] text-[var(--text-secondary)]">
+            {transportBadge}
+          </span>
+        </button>
+        <button
+          onClick={() => { if (confirm(`Remove MCP server "${server.name}"?`)) onRemove(server.id); }}
+          className="text-xs px-2 py-0.5 text-[var(--error)] hover:bg-[var(--bg-secondary)] rounded transition-colors"
+        >
+          Remove
+        </button>
+      </div>
+
+      {/* Expanded config */}
+      {expanded && (
+        <div className="px-3 pb-3 space-y-2 border-t border-[var(--border-color)] pt-2">
+          {/* Name */}
+          <div>
+            <label className="block text-xs text-[var(--text-secondary)] mb-0.5">Name</label>
+            <input
+              value={name}
+              onChange={(e) => setName(e.target.value)}
+              onBlur={handleNameBlur}
+              className={inputCls}
+            />
+          </div>
+
+          {/* Transport type */}
+          <div>
+            <label className="block text-xs text-[var(--text-secondary)] mb-0.5">Transport</label>
+            <div className="flex items-center gap-1">
+              {(["stdio", "http", "sse"] as McpTransportType[]).map((t) => (
+                <button
+                  key={t}
+                  onClick={() => handleTransportChange(t)}
+                  className={`px-2 py-0.5 text-xs rounded transition-colors ${
+                    transportType === t
+                      ? "bg-[var(--accent)] text-white"
+                      : "text-[var(--text-secondary)] hover:text-[var(--text-primary)] hover:bg-[var(--bg-secondary)]"
+                  }`}
+                >
+                  {t === "stdio" ? "Stdio" : t === "http" ? "HTTP" : "SSE"}
+                </button>
+              ))}
+            </div>
+          </div>
+
+          {/* Stdio fields */}
+          {transportType === "stdio" && (
+            <>
+              <div>
+                <label className="block text-xs text-[var(--text-secondary)] mb-0.5">Command</label>
+                <input
+                  value={command}
+                  onChange={(e) => setCommand(e.target.value)}
+                  onBlur={handleCommandBlur}
+                  placeholder="npx"
+                  className={inputCls}
+                />
+              </div>
+              <div>
+                <label className="block text-xs text-[var(--text-secondary)] mb-0.5">Arguments (space-separated)</label>
+                <input
+                  value={args}
+                  onChange={(e) => setArgs(e.target.value)}
+                  onBlur={handleArgsBlur}
+                  placeholder="-y @modelcontextprotocol/server-filesystem /path"
+                  className={inputCls}
+                />
+              </div>
+              <KeyValueEditor
+                label="Environment Variables"
+                pairs={envPairs}
+                onChange={(pairs) => { setEnvPairs(pairs); }}
+                onSave={saveEnv}
+              />
+            </>
+          )}
+
+          {/* HTTP/SSE fields */}
+          {(transportType === "http" || transportType === "sse") && (
+            <>
+              <div>
+                <label className="block text-xs text-[var(--text-secondary)] mb-0.5">URL</label>
+                <input
+                  value={url}
+                  onChange={(e) => setUrl(e.target.value)}
+                  onBlur={handleUrlBlur}
+                  placeholder="http://localhost:3000/mcp"
+                  className={inputCls}
+                />
+              </div>
+              <KeyValueEditor
+                label="Headers"
+                pairs={headerPairs}
+                onChange={(pairs) => { setHeaderPairs(pairs); }}
+                onSave={saveHeaders}
+              />
+            </>
+          )}
+        </div>
+      )}
+    </div>
+  );
+}
+
+function KeyValueEditor({
+  label,
+  pairs,
+  onChange,
+  onSave,
+}: {
+  label: string;
+  pairs: [string, string][];
+  onChange: (pairs: [string, string][]) => void;
+  onSave: (pairs: [string, string][]) => void;
+}) {
+  const inputCls = "flex-1 min-w-0 px-2 py-1 bg-[var(--bg-primary)] border border-[var(--border-color)] rounded text-xs text-[var(--text-primary)] focus:outline-none focus:border-[var(--accent)]";
+
+  return (
+    <div>
+      <label className="block text-xs text-[var(--text-secondary)] mb-0.5">{label}</label>
+      {pairs.map(([key, value], i) => (
+        <div key={i} className="flex gap-1 items-center mb-1">
+          <input
+            value={key}
+            onChange={(e) => {
+              const updated = [...pairs] as [string, string][];
+              updated[i] = [e.target.value, value];
+              onChange(updated);
+            }}
+            onBlur={() => onSave(pairs)}
+            placeholder="KEY"
+            className={inputCls}
+          />
+          <span className="text-xs text-[var(--text-secondary)]">=</span>
+          <input
+            value={value}
+            onChange={(e) => {
+              const updated = [...pairs] as [string, string][];
+              updated[i] = [key, e.target.value];
+              onChange(updated);
+            }}
+            onBlur={() => onSave(pairs)}
+            placeholder="value"
+            className={inputCls}
+          />
+          <button
+            onClick={() => {
+              const updated = pairs.filter((_, j) => j !== i);
+              onChange(updated);
+              onSave(updated);
+            }}
+            className="flex-shrink-0 px-1.5 py-1 text-xs text-[var(--error)] hover:bg-[var(--bg-secondary)] rounded transition-colors"
+          >
+            x
+          </button>
+        </div>
+      ))}
+      <button
+        onClick={() => {
+          onChange([...pairs, ["", ""]]);
+        }}
+        className="text-xs text-[var(--accent)] hover:text-[var(--accent-hover)] transition-colors"
+      >
+        + Add
+      </button>
+    </div>
+  );
+}