ux: in-app confirm for asset/sitesmith delete + safe copy

- AssetsPanel: asset delete now requires an in-app two-step confirm
  (tile-button turns into "Delete?" + cancel, auto-resets after 4s or on
  click-elsewhere) instead of deleting with no confirmation at all.
- AssetsPanel: copyUrl uses a new copyToClipboard() helper that tries the
  async Clipboard API and falls back to a hidden-textarea execCommand copy
  in non-secure contexts, surfacing a visible "Copy failed" state instead
  of silently doing nothing.
- SitesmithModal: replaced window.confirm(...) for "Clear chat" with the
  same in-app two-step confirm pattern -- no native dialogs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/panels/sitesmith/SitesmithModal.tsx

@@ -1,4 +1,4 @@
-import React, { useState } from 'react';
+import React, { useState, useRef, useEffect } from 'react';
 import { useEditor } from '@craftjs/core';
 import { useEditorConfig } from '../../state/EditorConfigContext';
 import { useSitesmith } from '../../hooks/useSitesmith';
@@ -28,6 +28,14 @@ export const SitesmithModal: React.FC<Props> = ({ onClose, target }) => {
   const [busy, setBusy] = useState(false);
   const [pendingReplace, setPendingReplace] = useState<SitesmithResponse | null>(null);
   const [error, setError] = useState<string | null>(null);
+  const [confirmClearChat, setConfirmClearChat] = useState(false);
+  const clearChatTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+
+  useEffect(() => {
+    return () => {
+      if (clearChatTimeoutRef.current) clearTimeout(clearChatTimeoutRef.current);
+    };
+  }, []);
 
   const canChat = summary && (summary.status === 'OK_BONUS' || summary.status === 'OK_MONTHLY');
 
@@ -67,6 +75,23 @@ export const SitesmithModal: React.FC<Props> = ({ onClose, target }) => {
     if (!r.ok) setError(r.message || 'Apply failed');
   };
 
+  const cancelClearChat = () => {
+    if (clearChatTimeoutRef.current) clearTimeout(clearChatTimeoutRef.current);
+    setConfirmClearChat(false);
+  };
+
+  const handleClearChatClick = async () => {
+    if (!confirmClearChat) {
+      setConfirmClearChat(true);
+      if (clearChatTimeoutRef.current) clearTimeout(clearChatTimeoutRef.current);
+      clearChatTimeoutRef.current = setTimeout(() => setConfirmClearChat(false), 4000);
+      return;
+    }
+    cancelClearChat();
+    const r = await clearHistory();
+    if (!r.ok) setError(r.error || 'Failed to clear history');
+  };
+
   return (
     <div role="dialog" aria-modal="true" style={overlay}>
       <div style={panel}>
@@ -80,17 +105,29 @@ export const SitesmithModal: React.FC<Props> = ({ onClose, target }) => {
           )}
           <div style={{ flex: 1 }} />
           {messages.length > 0 && (
-            <button
-              onClick={async () => {
-                if (!window.confirm('Clear all Sitesmith chat history for this site? The canvas is unaffected.')) return;
-                const r = await clearHistory();
-                if (!r.ok) setError(r.error || 'Failed to clear history');
-              }}
-              style={clearBtn}
-              title="Clear chat history"
-            >
-              Clear chat
-            </button>
+            confirmClearChat ? (
+              <>
+                <button
+                  onClick={handleClearChatClick}
+                  style={{ ...clearBtn, background: '#b91c1c', color: '#fff', borderColor: '#b91c1c' }}
+                  title="Click again to permanently clear chat history"
+                  autoFocus
+                >
+                  Confirm clear?
+                </button>
+                <button onClick={cancelClearChat} style={clearBtn} title="Cancel">
+                  Cancel
+                </button>
+              </>
+            ) : (
+              <button
+                onClick={handleClearChatClick}
+                style={clearBtn}
+                title="Clear all Sitesmith chat history for this site (canvas is unaffected)"
+              >
+                Clear chat
+              </button>
+            )
           )}
           <button onClick={onClose} aria-label="Close" style={closeBtn}>✕</button>
         </div>