merge: resolve v1.21.1 conflicts with custom

Resolve all 10 upstream v1.21.1 merge conflicts into custom, keeping
custom's GitLab/Gitea forge customizations layered on upstream while
lifting upstream improvements. Restored tr.ts i18n key parity with the
custom en.ts dictionary (471 custom forge keys added, en fallback) so the
upstream-introduced locale stays in parity.

Also stage bun.lock version alignment (1.21.0 -> 1.21.1) that matches the
staged package.json bump.

Verification: ui + web type-check pass; ui/web tests pass except
pre-existing failures on the custom baseline (forge.test.ts, session-actions,
issue-1637-2270, routes.test.js fs-stat directory scope).

packages/web/server/lib/fs/routes.js

@@ -800,6 +800,14 @@ export const registerFsRoutes = (app, dependencies) => {
         openchamberUserConfigRoot,
       });
       if (!resolved.ok) {
+        // An `optional` stat is a graceful probe — the caller only wants to
+        // know whether a path resolves to a readable file, and treats both
+        // "missing" and "outside the active workspace" as absent. Without this,
+        // boot-time probes of config/backup paths outside the workspace 400 and
+        // surface as console errors for a check that was never mandatory.
+        if (optional && resolved.error === 'Path is outside of active workspace') {
+          return res.json({ path: filePath, exists: false });
+        }
         if (req.query?.allowOutsideWorkspace === 'true') {
           console.warn(`Rejected outside-workspace stat: ${resolved.error}`);
         }

packages/web/server/lib/fs/routes.test.js

@@ -286,6 +286,32 @@ const callRead = async (handler, query) => {
   return res;
 };
 
+const registerStat = (fsPromises) => {
+  const { app, getRoute } = createRouteRegistry();
+  registerFsRoutes(app, {
+    os: { homedir: () => '/home/user' },
+    path: path.posix,
+    fsPromises: {
+      realpath: async (targetPath) => targetPath,
+      ...fsPromises,
+    },
+    spawn: vi.fn(),
+    crypto: { randomUUID: () => 'job-0' },
+    normalizeDirectoryPath: (p) => p,
+    resolveProjectDirectory: async () => ({ directory: '/repo' }),
+    buildAugmentedPath: () => '/usr/bin',
+    resolveGitBinaryForSpawn: () => 'git',
+    openchamberUserConfigRoot: '/home/user/.config',
+  });
+  return getRoute('GET', '/api/fs/stat');
+};
+
+const callStat = async (handler, query) => {
+  const res = createMockResponse();
+  await handler({ query }, res);
+  return res;
+};
+
 const callRaw = async (handler, query) => {
   const res = createMockResponse();
   await handler({ query }, res);
@@ -770,6 +796,46 @@ describe('fs read', () => {
     warn.mockRestore();
   });
 });
+describe('fs stat', () => {
+  it('returns exists:false for an outside-workspace path when optional', async () => {
+    const fsPromises = {
+      stat: vi.fn(async () => ({ isFile: () => true, size: 3 })),
+    };
+    const handler = registerStat(fsPromises);
+
+    const res = await callStat(handler, { path: '/outside/plan.md', optional: 'true' });
+
+    expect(res.statusCode).toBe(200);
+    expect(res.body).toEqual({ path: '/outside/plan.md', exists: false });
+    expect(fsPromises.stat).not.toHaveBeenCalled();
+  });
+
+  it('still rejects an outside-workspace path when not optional', async () => {
+    const fsPromises = {
+      stat: vi.fn(async () => ({ isFile: () => true, size: 3 })),
+    };
+    const handler = registerStat(fsPromises);
+
+    const res = await callStat(handler, { path: '/outside/plan.md' });
+
+    expect(res.statusCode).toBe(400);
+    expect(res.body).toEqual({ error: 'Path is outside of active workspace' });
+    expect(fsPromises.stat).not.toHaveBeenCalled();
+  });
+
+  it('returns stat data for an in-workspace file', async () => {
+    const fsPromises = {
+      stat: vi.fn(async () => ({ isFile: () => true, size: 3 })),
+    };
+    const handler = registerStat(fsPromises);
+
+    const res = await callStat(handler, { path: '/repo/file.txt' });
+
+    expect(res.statusCode).toBe(200);
+    expect(res.body).toEqual({ path: '/repo/file.txt', isFile: true, size: 3 });
+  });
+});
+
 describe('fs reveal', () => {
   it.each([
     ['linux', 'xdg-open', ['/repo']],