feat: collaboration temps reel - edition simultanee (#62)

WebSocket /ws/collab/{vault}/{path} (rooms par fichier), relais Yjs/CRDT, awareness (curseurs colores + presence), persistance serveur debounce 2s, auth WS + check_vault_access, reconnexion automatique. Frontend frontend/js/collab.js, backend backend/collab.py. Tests: 17 backend (5 clients simultanes) + 10 frontend. Docs: CHANGELOG, ROADMAP, fiche features/collaboration.md, README FR/EN.

.gitea/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
       - name: Frontend unit tests
         run: node tests/frontend/unit.test.mjs
 
-      - name: Frontend JSDOM tests (PaneManager + Excalidraw + Plugins + AI + SW)
+      - name: Frontend JSDOM tests (PaneManager + Excalidraw + Plugins + AI + SW + Collab)
         run: |
           cd tests/frontend
           if [ -d node_modules ]; then
@@ -47,6 +47,7 @@ jobs:
             node plugins.test.mjs
             node ai.test.mjs
             node sw.test.mjs
+            node collab.test.mjs
           else
             echo "tests/frontend/node_modules missing — installing jsdom"
             npm install --no-audit --no-fund --silent
@@ -55,6 +56,7 @@ jobs:
             node plugins.test.mjs
             node ai.test.mjs
             node sw.test.mjs
+            node collab.test.mjs
           fi
 
   # ── Tests ─────────────────────────────────────────────────────────