docs(plans): add theme-registry + flowchart-editor implementation plans

Two step-by-step TDD plans derived from the 2026-09-14 design specs:

* theme-registry: 9 tasks, 70+ steps. Creates src/main/ThemeRegistry.js
  (pure module), bootstrap with 37 themes, buildThemeMenu for main.js,
  migrates 25 existing per-theme CSS blocks into src/styles/themes/<id>.css,
  rewrites the renderer apply-theme function to toggle <link disabled>,
  adds 12 new theme CSS files using shared token vocabulary.
* flowchart-editor: 8 tasks, 41 TDD steps. Pure renderer-side feature
  (no main-process modules). Pure data store with IO injection, 5 SVG
  shape functions, Mermaid translator, hand-rolled SVG canvas with
  pointer events, sidebar panel wiring with debounced preview (250ms)
  + debounced persistence (500ms) + panel-scoped keyboard shortcuts.
  Three minimal userData-path-validated IPC channels added for
  persistence (renderer can't reach <userData> under the current
  nodeIntegration:true security model without them).

Amit Haridas

.github/workflows/release.yml

@@ -68,9 +68,27 @@ jobs:
 
       - name: Bundle MarkItDown (optional, best effort)
         # Windows runners ship python + venv; non-fatal on failure — the
-        # package then omits the bundled binary by design
-        run: npm run bundle:markitdown
+        # package then omits the bundled binary by design. We capture the
+        # log so a silent failure is visible in the GitHub Actions step UI
+        # instead of disappearing into stdout.
+        run: |
+          python -m pip install --upgrade pip wheel setuptools 2>&1 | tee bundle-pip.log
+          npm run bundle:markitdown 2>&1 | tee bundle-markitdown.log
+          if [ ! -f bin/win32/markitdown.exe ]; then
+            echo "::warning::bin/win32/markitdown.exe was not produced — see bundle-markitdown.log"
+          fi
         continue-on-error: true
+        shell: bash
+
+      - name: Upload MarkItDown bundle logs (on failure)
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: windows-bundle-logs
+          path: |
+            bundle-pip.log
+            bundle-markitdown.log
+          retention-days: 5
 
       - name: Run tests
         run: npm test