docs: reorg examples folder under new IA (SD-2881) (#3055)

* docs: reorg examples folder under new IA (SD-2881)

Move examples to mirror the docs IA (Editor / Document Engine / AI),
matching the post-SD-2873 doc structure. Developers reading a Custom UI
or Built-in UI page can now click into a parallel examples folder.

Editor:
- examples/features/comments to examples/editor/built-in-ui/comments
- examples/features/track-changes to examples/editor/built-in-ui/track-changes
- examples/features/custom-toolbar to examples/editor/built-in-ui/toolbar
- examples/features/theming to examples/editor/theming
- examples/features/spell-check to examples/editor/proofing
- examples/collaboration/{liveblocks,hocuspocus,superdoc-yjs} to
  examples/editor/collaboration/providers/*
- examples/collaboration/{node-sdk,fastapi} to
  examples/editor/collaboration/backends/*

Document Engine:
- examples/features/diffing to examples/document-engine/diffing

AI:
- examples/features/ai-redlining to examples/ai/redlining
- examples/collaboration/ai-node-sdk to examples/ai/collaborative-agent

Cascading updates:
- examples/__tests__/playwright.config.ts: portMap and useConcurrently
  list updated to new paths.
- pnpm-workspace.yaml: add examples/*/*/*/* glob (collaboration providers
  are now four levels deep).
- Doc cross-references swept to new example paths across editor,
  proofing, collaboration, and AI pages.
- Replace two stale Resources cards in superdoc-yjs.mdx that pointed
  at examples/collaboration/{production,fastify-server} (never existed)
  with real targets.
- Rewrite examples/README.md as a navigable index that mirrors the new
  structure.

* fix(docs): update FastAPI README cd paths after reorg (SD-2881)

Codex flagged that the README in
examples/editor/collaboration/backends/fastapi/ still told users to
`cd examples/collaboration/fastapi` after the path moved. Following
the documented steps would fail with 'No such file or directory'.
Update the cd commands in this README and its nested yjs-hub/README.md
to the new IA path.

* fix(ci+examples): finish reorg cascading updates (SD-2881)

Codex review on PR #3055 surfaced four cascading-update gaps the reorg
left behind. Fix all four.

CI workflow (.github/workflows/ci-examples.yml):
- collaboration job: working-directory and EXAMPLE both pointed at
  examples/collaboration/* (gone). Update to
  examples/editor/collaboration/providers/*.
- features job: split into two jobs that match the new IA.
  built-in-ui (track-changes, comments, toolbar) targets
  examples/editor/built-in-ui/*; ai (redlining) targets
  examples/ai/*. ai-redlining moved to examples/ai/redlining and
  custom-toolbar to examples/editor/built-in-ui/toolbar in the reorg,
  so the matrix shape changes too.
- validate job needs list updated to the new job names.
- headless job working-directory unchanged: examples/headless/ai-redlining
  still exists at the same path.

Workspace globs (pnpm-workspace.yaml):
- yjs-hub now sits at examples/editor/collaboration/backends/fastapi/
  yjs-hub, five segments below examples/. The previous deepest glob
  was four. Add an examples/*/*/*/*/* glob so the package is picked up
  by pnpm install --frozen-lockfile.

Liveblocks Python smoke (examples/editor/collaboration/providers/
liveblocks/scripts/smoke-python-sdk.py):
- Path(__file__).resolve().parents[4] used to point at the repo root
  when the script lived three directories below the repo. After the
  move to providers/liveblocks/scripts, parents[4] now points at
  examples/editor. Update to parents[6] to keep REPO_ROOT correct.

READMEs and prose:
- examples/editor/collaboration/backends/node-sdk/README.md: cd
  commands updated from /examples/collaboration/{node-sdk,fastapi} to
  /examples/editor/collaboration/backends/{node-sdk,fastapi}.
- liveblocks README + smoke script and fastapi README: stale prose
  references to examples/collaboration/* paths swept to the new
  locations.

Author: caio-pizzol

.github/workflows/ci-examples.yml

@@ -104,23 +104,23 @@ jobs:
           key: examples-workspace-${{ github.sha }}
 
       - name: Create .env for cloud providers
-        working-directory: examples/collaboration/${{ matrix.example }}
+        working-directory: examples/editor/collaboration/providers/${{ matrix.example }}
         run: |
           if [ "${{ matrix.example }}" = "liveblocks" ]; then
             echo "VITE_LIVEBLOCKS_PUBLIC_KEY=${{ secrets.VITE_LIVEBLOCKS_PUBLIC_KEY }}" > .env
           fi
 
       - name: Run smoke test
         working-directory: examples/__tests__
-        run: EXAMPLE=collaboration/${{ matrix.example }} npx playwright test
+        run: EXAMPLE=editor/collaboration/providers/${{ matrix.example }} npx playwright test
 
-  features:
+  built-in-ui:
     needs: build
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
-        example: [track-changes, ai-redlining, comments, custom-toolbar]
+        example: [track-changes, comments, toolbar]
     steps:
       - name: Restore workspace
         uses: actions/cache/restore@v4
@@ -132,7 +132,27 @@ jobs:
 
       - name: Run smoke test
         working-directory: examples/__tests__
-        run: EXAMPLE=features/${{ matrix.example }} npx playwright test
+        run: EXAMPLE=editor/built-in-ui/${{ matrix.example }} npx playwright test
+
+  ai:
+    needs: build
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        example: [redlining]
+    steps:
+      - name: Restore workspace
+        uses: actions/cache/restore@v4
+        with:
+          path: |
+            .
+            ~/.cache/ms-playwright
+          key: examples-workspace-${{ github.sha }}
+
+      - name: Run smoke test
+        working-directory: examples/__tests__
+        run: EXAMPLE=ai/${{ matrix.example }} npx playwright test
 
   advanced-headless-toolbar:
     needs: build
@@ -173,7 +193,7 @@ jobs:
   validate:
     name: CI Examples / validate
     if: always()
-    needs: [getting-started, collaboration, features, advanced-headless-toolbar, headless]
+    needs: [getting-started, collaboration, built-in-ui, ai, advanced-headless-toolbar, headless]
     runs-on: ubuntu-latest
     steps:
       - name: Check results