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/projects/home/ContainerMigrationBanner.test.tsx

@@ -18,6 +18,7 @@ const FRESH: ContainerStaleness = {
   apt_delta: [],
   npm_global_delta: [],
   verbatim_paths: [],
+  unpreserved_data: [],
   outdated_package_count: 0,
   probe_error: null,
 };
@@ -40,6 +41,7 @@ function migration(overrides: Partial<ContainerMigration> = {}): ContainerMigrat
   return {
     staleness: null,
     probing: false,
+    probeSettled: true,
     running: false,
     recovered: false,
     interrupted: null,
@@ -51,7 +53,7 @@ function migration(overrides: Partial<ContainerMigration> = {}): ContainerMigrat
     resume: vi.fn(async () => {}),
     keep: vi.fn(async () => {}),
     rollback: vi.fn(async () => {}),
-    dismiss: vi.fn(),
+    dismiss: vi.fn(async () => {}),
     refresh: vi.fn(async () => {}),
     ...overrides,
   };
@@ -173,7 +175,7 @@ describe("ContainerMigrationBanner", () => {
     });
     renderBanner(m);
     expect(
-      screen.getByText(/A container base update was interrupted/i),
+      screen.getByText(/The container base update did not finish/i),
     ).toBeInTheDocument();
     expect(screen.getByText(/part-way onto the new base/i)).toBeInTheDocument();
     // The plain "Update container base…" call to action must not be what is
@@ -207,6 +209,36 @@ describe("ContainerMigrationBanner", () => {
     expect(screen.getByRole("button", { name: "Resume update" })).toBeInTheDocument();
   });
 
+  it("distinguishes an unsettled probe from a running container", () => {
+    // "Stop the container to update its base" on a container that is already
+    // stopped — because the probe has not landed — reads as a bug.
+    renderBanner(
+      migration({ staleness: STALE, probing: true, probeSettled: false }),
+      false,
+    );
+    expect(
+      screen.getByText(/Checking what this container has/i),
+    ).toBeInTheDocument();
+    expect(
+      screen.queryByText(/Stop the container to update its base/i),
+    ).not.toBeInTheDocument();
+  });
+
+  it("names the /var data that updating would destroy", () => {
+    renderBanner(
+      migration({
+        staleness: {
+          ...STALE,
+          unpreserved_data: [
+            { path: "/var/lib/postgresql", bytes: 41_000_000, file_count: 912 },
+          ],
+        },
+      }),
+    );
+    expect(screen.getByText("/var/lib/postgresql")).toBeInTheDocument();
+    expect(screen.getByText(/back this up before updating/i)).toBeInTheDocument();
+  });
+
   describe("the report", () => {
     const CLEAN: MigrationReport = {
       phase: "succeeded",
@@ -295,6 +327,39 @@ describe("ContainerMigrationBanner", () => {
       expect(screen.getByRole("button", { name: "Dismiss" })).toBeInTheDocument();
     });
 
+    it("never offers Keep over a container that is still mid-swap", () => {
+      // The failing-commit path returns a report *and* leaves the record
+      // interrupted. Keep would untag the rollback image and delete the record
+      // while `triple-c-snapshot-<id>:latest` still points at the old lineage —
+      // and the backend's own message on that record says to resume.
+      const m = migration({
+        staleness: STALE,
+        interrupted: {
+          phase: "interrupted",
+          from_image_id: "sha256:aaa",
+          to_base_id: "sha256:bbb",
+          started_at: "2026-08-09T10:00:00Z",
+          report: null,
+          rollback_image: "triple-c-snapshot-p1:pre-migration-20260809-100000",
+          staging_path: null,
+          options: { replay_packages: true, copy_paths: true, keep_rollback: true },
+          plan: null,
+        },
+        report: {
+          ...CLEAN,
+          phase: "failed",
+          message: "saving it failed. Resume it, or roll back.",
+        },
+      });
+      renderBanner(m);
+      expect(screen.queryByRole("button", { name: "Keep" })).not.toBeInTheDocument();
+      expect(
+        screen.getByRole("button", { name: "Resume update" }),
+      ).toBeInTheDocument();
+      fireEvent.click(screen.getByRole("button", { name: "Roll back" }));
+      expect(m.rollback).toHaveBeenCalledTimes(1);
+    });
+
     it("does not describe rollback as a time machine", () => {
       renderBanner(migration({ staleness: FRESH, report: CLEAN }));
       expect(