Initial commit: opencode_bridge JupyterLab extension (Slices 1-3.5)

A JupyterLab extension that bridges the cell UI to a local OpenCode Serve
process. The extension is a dual package: a Python server extension
exposed under /opencode-bridge/*, plus a TypeScript frontend that
registers per-cell toolbars.

Backend (Python, tornado)
- Slice 1: config + auth + OpenCode HTTP client (tornado.httpclient,
  no aiohttp). 4 settings in schema/plugin.json (url, user, password,
  request timeout).
- Slice 2: handlers for /hello, /health, /providers, /edit.
- Slice 2.1 (correction): SessionManager with 1 notebook = 1 session
  mapping, async-safe via per-path locks, 404 recovery via invalidate().
  Two new endpoints: GET /sessions, DELETE /session?notebook=<path>.
- 32 pytest tests pass.

Frontend (TypeScript, JupyterLab 4.6)
- src/types.ts: CellContext, OpenCodeRequest/Response, OpenCodeSettings.
- src/context/cell_context.ts: extract CellContext from a CodeCell +
  its parent NotebookPanel, structured error collection.
- src/api/opencode_client.ts: callOpenCodeEdit, callOpenCodeProviders.
- src/components/opencode_cell_footer.ts: OpenCodeCellFooter Widget
  implementing ICellFooter with 3 buttons (optimize / fix / edit),
  resolved via this.parent instanceof CodeCell. NOT cellToolbar
  (does not exist in JL 4.6) and NOT Widget.findParent (removed in
  @lumino/widgets 2.x).
- src/components/opencode_cell_factory.ts: Cell.ContentFactory
  subclass returning the OpenCodeCellFooter.
- src/components/opencode_installer.ts: installOpenCodeEverywhere
  patches every notebook (existing + new) to use the custom factory.
- src/index.ts: registers the factory, loads settings, fetches
  /providers on activation and logs the list to the console.
- 23 jest tests pass (mocked JupyterLab boundary, pnpm path safe).

Settings
- 6 fields: 3 auth (url/user/password) + 1 timeout + 2 model selection
  (provider/model). Provider list is fetched at startup from
  /opencode-bridge/providers and printed to the browser console so
  users can copy values into Settings Editor.

Docs
- design.md: 6 sections covering architecture, UI flow, API contract,
  TS skeletons, session management (v0.2.1 correction), and
  provider/model selection (v0.2.2 addition).
- CLAUDE.md: agent guidance for working in this repo.
- TODO.md: remaining work for Slices 4-7 + v0.4+ backlog.

CI
- Gitea release workflow at .github/workflows/build.yml.
- Bark notification helper (non-fatal on failure).

Generated artefacts ignored: opencode_bridge/labextension/, _version.py,
*.tsbuildinfo, junit.xml, test.ipynb scratch notebook.

.github/workflows/build.yml

@@ -0,0 +1,64 @@
+name: CI
+
+on:
+  push:
+#    branches:
+#      - main
+    tags:
+      - 'v*'
+  pull_request:
+
+jobs:
+  ci:
+    name: CI
+    # Standard GitHub-hosted ubuntu runner. uv is installed via the
+    # astral-sh/setup-uv action (one extra step vs. using a self-hosted
+    # runner with uv pre-installed, but matches what GitHub-hosted CI
+    # provides out of the box).
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up uv
+        uses: https://github.com/astral-sh/setup-uv@v6
+        with:
+          enable-cache: true
+
+      - name: Build package
+        env:
+          # Use the Tsinghua PyPI mirror for build-environment resolution;
+          # the runner is in China and the default pypi.org is too slow
+          # / unreliable for build dependency install.
+          UV_DEFAULT_INDEX: "https://pypi.tuna.tsinghua.edu.cn/simple/"
+        run: uv build
+
+      # Only create a release + attach dist/ assets when pushing a v* tag.
+      # On branch pushes / pull requests this step is skipped entirely.
+      # The release logic is in a separate script to avoid embedding a JSON
+      # heredoc inside a YAML block scalar (the previous version of this
+      # step was rejected by Gitea's YAML parser at line 51).
+      - name: Upload release assets via Gitea API
+        if: startsWith(github.ref, 'refs/tags/v')
+        env:
+          GITEA_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          TAG_NAME: ${{ github.ref_name }}
+          API_URL: ${{ github.api_url }}
+          REPOSITORY: ${{ github.repository }}
+          SHA: ${{ github.sha }}
+        run: ./.github/scripts/create-release.sh
+
+      # Always run, regardless of job status. The script is a side-effect;
+      # if the notification itself fails we swallow the error so CI does
+      # not turn red on a Bark outage.
+      - name: Notify Bark
+        if: always()
+        run: |
+          if [ "${{ job.status }}" = "success" ]; then
+            TITLE="✅ CI: ${{ github.repository }}@${{ github.ref_name }}"
+            BODY="Build OK for ${{ github.sha }} by ${{ github.actor }}"
+          else
+            TITLE="❌ CI: ${{ github.repository }}@${{ github.ref_name }}"
+            BODY="Build FAILED for ${{ github.sha }} by ${{ github.actor }}"
+          fi
+          ./.github/scripts/bark-notify.sh "$TITLE" "$BODY" || echo "Bark notify failed (non-fatal)"