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/docs/content/docs/gitlab.mdx

@@ -0,0 +1,31 @@
+---
+title: GitLab Issues & MRs
+description: Connect GitLab and start sessions from issues and merge requests.
+---
+
+# GitLab Issues & MRs
+
+Connect your GitLab account and OpenChamber can pull in issues and merge requests, and start a session straight from one. You can also create, update, and merge MRs directly from OpenChamber.
+
+## Connect GitLab
+
+1. Open **Settings → Git**.
+2. Under GitLab, choose **Connect**.
+3. Paste a Personal Access Token. Create one in GitLab under **Profile → Access Tokens** — the `read_api` scope is enough for read-only workflows, and `api` is needed later for writing.
+4. For a self-hosted GitLab instance, also enter the instance URL (for example `https://gitlab.example.com`).
+
+When it's connected, your account shows under the GitLab section. You can connect more than one account and switch between them, or disconnect at any time.
+
+## Start work from an issue or MR
+
+When you create a [worktree session](/worktrees/) with GitLab connected, you can choose **Start from GitLab issue/MR**:
+
+- pick an **issue** and OpenChamber names the branch after it and opens the session with the issue and its comments as the first message
+- pick a **merge request** and it checks out the MR's branch; you can include the MR's diff so the agent has the full change
+
+This drops you straight into a session with the context already loaded.
+
+## Related
+
+- [Git & GitHub Workflows](/git/) — commit and manage branches
+- [Worktree Sessions](/worktrees/) — where issue and MR sessions start

packages/docs/sidebar.config.json

@@ -308,6 +308,21 @@
             "tr": "GitHub issue'ları ve PR'lar"
           }
         },
+        {
+          "label": "GitLab Issues & MRs",
+          "link": "/gitlab/",
+          "translations": {
+            "uk": "Завдання та MR GitLab",
+            "zh-CN": "GitLab 工单与 MR",
+            "es": "Issues y MRs de GitLab",
+            "pt-BR": "Issues e MRs do GitLab",
+            "ko": "GitLab 이슈 및 MR",
+            "pl": "Zgłoszenia i MR-y GitLab",
+            "fr": "Issues et MR GitLab",
+            "ja": "GitLab Issues と MR",
+            "de": "GitLab-Issues und MRs"
+          }
+        },
         {
           "label": "Magic Prompts",
           "link": "/magic-prompts/",