feat: groupes de travail (P5)

Ajoute la notion de groupe — collection nommée de repos (membership légère
persistée, many-to-many) — pour piloter plusieurs repos en simultané :

- DB : migration #5 (tables groups + group_repos, FK ON DELETE CASCADE).
- GroupManager (synchrone, EventEmitter) + routes REST /api/v1/groups ;
  ne persiste que la membership, worktrees/sessions filtrés par repoId côté client.
- Protocole : GroupSummary, DTOs, topic WS « groups », events group_update/removed
  (additifs, PROTOCOL_VERSION inchangé).
- Web : store groups, GroupsListView, GroupView (réutilise RepoSection),
  grille multi-terminaux (TerminalGrid/TerminalCell), action « feature cross-repo »
  (orchestration client, tolérante aux échecs partiels), routes + i18n EN/FR.
- Tests : group-manager.test.ts + extension protocol.test.ts ; acceptance-p5.mjs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/web/src/lib/api.ts

@@ -34,5 +34,6 @@ async function request<T>(path: string, method: string, body?: unknown): Promise
 export const api = {
   get: <T>(path: string): Promise<T> => request<T>(path, 'GET'),
   post: <T>(path: string, body?: unknown): Promise<T> => request<T>(path, 'POST', body),
+  patch: <T>(path: string, body?: unknown): Promise<T> => request<T>(path, 'PATCH', body),
   delete: <T>(path: string): Promise<T> => request<T>(path, 'DELETE'),
 };