Fix review findings: secrets in snapshots, URL spoofing, migration data loss

Adversarial review of the branch produced findings across four areas.
This addresses them, plus the Windows CI environment.

Secrets. commit_container_snapshot baked the container's full env into
the per-project snapshot image, so the shared OAuth token — and the AWS
keys, git token and gateway master key — outlived revocation and were
readable via docker inspect. Verified against Engine 29.6 that a commit
body's config merges over the container's: keys cannot be dropped but
can be overwritten, so all of them now commit as KEY=. clear_claude_token
additionally rewrites images from earlier builds and reports honestly
when a tag could not be rewritten.

The recommendation to move the token out of env entirely was not taken,
with reasoning: apiKeyHelper is a different auth method that outranks
CLAUDE_CODE_OAUTH_TOKEN rather than a transport for it, and no
file-based delivery exists. The durable exposure — the image — is what
is closed here. Separately noted, not fixed: entrypoint.sh captures the
token into the scheduler's .env inside the persisted volume.

URL spoofing. Three call sites reached openUrl with container-controlled
strings, one of which the review missed (the WebLinksAddon handler).
The sign-in URL was scraped from container output with a longest-match
tie-break and no userinfo check, so claude.ai@evil.tld rendered as
"claude.ai…" in a truncating element. There is now one sanitizer in
front of every sink — scheme allowlist, no userinfo, C0/C1 and quote
rejection, host allowlist for the sign-in case, first-match — and the
origin renders un-truncated. The toast is keyed so a changed URL
remounts, closing a bait-and-switch where the user read one URL and
clicked another.

Migration. The rollback pin was best-effort: a tag failure was logged
and the migration continued past remove_container, after which the
final commit overwrote the only copy of the old system layer. It now
aborts before anything destructive and reads the tag back. /var was
destroyed while the ordinary recreate path preserves it — making the
"safe" alternative to Reset more destructive than Reset's alternative;
data-bearing subtrees are now detected and disclosed in the pre-flight
rather than copied, since tarring a live database onto a different
base's packages is a corruption risk. resume_migration now verifies the
migration-state label instead of reporting success for a container that
never swapped. dismiss actually resolves the record rather than leaving
the feature permanently refusing to migrate. Start and Reset are guarded
while a migration is live.

Lifecycle. The gateway no longer publishes on 0.0.0.0 — bind address and
advertised URL are derived together so they cannot drift. Disabling it
now stops it. App exit runs teardown concurrently under a budget with a
visible shutting-down state instead of blocking for minutes. Auto-starts
retry when Docker is not up yet, and the polling-recovery path now
reconciles, so interrupted migrations are still recovered. Auth-bridge
forwards are capped, closing a container-driven fd exhaustion.

Windows CI. build-windows failed on this branch with "linker link.exe
not found". The runner had no MSVC build tools and the workflow assumed
a hand-provisioned machine, so a bare runner registers, accepts jobs and
fails at link time after downloading the whole crate graph. The job now
installs the VC++ workload when vswhere cannot find it, matching how it
already conditionally installs Rust and Node.

192 Rust tests, 274 frontend tests, both builds clean, zero warnings.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/src/components/terminal/UrlToast.test.tsx

@@ -0,0 +1,61 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen } from "@testing-library/react";
+import UrlToast from "./UrlToast";
+
+/**
+ * The toast is the *only* thing standing between a container-chosen URL and
+ * the host's browser, so what it shows has to be what will be opened — and the
+ * part that decides that is the origin.
+ */
+describe("UrlToast", () => {
+  const noop = () => {};
+
+  it("shows the origin separately from the truncatable remainder", () => {
+    render(
+      <UrlToast
+        url="https://github.com/login/device?code=ABCD-EFGH"
+        onOpen={noop}
+        onDismiss={noop}
+      />,
+    );
+    expect(screen.getByTestId("url-toast-origin")).toHaveTextContent(
+      "https://github.com",
+    );
+    expect(screen.getByTestId("url-toast-rest")).toHaveTextContent(
+      "/login/device?code=ABCD-EFGH",
+    );
+  });
+
+  it("keeps the origin intact when the path is long enough to push it out", () => {
+    const url = `https://evil.tld/${"padding/".repeat(200)}end`;
+    render(<UrlToast url={url} onOpen={noop} onDismiss={noop} />);
+    // The registrable domain must be present in its own element, whole. A
+    // single ellipsised line would render this and show only the padding.
+    expect(screen.getByTestId("url-toast-origin")).toHaveTextContent(
+      "https://evil.tld",
+    );
+  });
+
+  it("exposes the whole URL as a tooltip", () => {
+    const url = "https://example.com/a/b?c=d";
+    render(<UrlToast url={url} onOpen={noop} onDismiss={noop} />);
+    expect(screen.getByTestId("url-toast-url")).toHaveAttribute("title", url);
+  });
+
+  it("announces itself, so a replacement prompt is not silent", () => {
+    render(
+      <UrlToast url="https://example.com/" onOpen={noop} onDismiss={noop} />,
+    );
+    expect(screen.getByRole("status")).toBeInTheDocument();
+  });
+
+  it("opens only via the button, never on its own", () => {
+    const onOpen = vi.fn();
+    render(
+      <UrlToast url="https://example.com/" onOpen={onOpen} onDismiss={noop} />,
+    );
+    expect(onOpen).not.toHaveBeenCalled();
+    screen.getByRole("button", { name: "Open" }).click();
+    expect(onOpen).toHaveBeenCalledTimes(1);
+  });
+});