feat(p10): archivage automatique des sessions terminées (rétention configurable)

- DB: migration #10 (sessions.archived_at + index), helpers archive/unarchive/archiveExpired (soft-archive, jamais de DELETE)
- core/retention-settings.ts: session_retention_days (défaut 30, 0=jamais, 1-3650) + session_purge_days (off)
- core/session-archive.ts: scheduler start/stop/sweep (calqué DiscoveryService), câblé dans runDaemon
- pty-manager.list({includeArchived}) + SessionSummary.archived + emitHistoricalUpdate
- routes: GET /sessions?includeArchived, POST/DELETE /sessions/:id/archive, POST /sessions/archive-now
- protocole additif: message WS session_archived (relayé par la gateway, abonnés 'sessions')
- settings: retentionDays/purgeDays exposés et validés dans PATCH /settings
- web: store sessions (showArchived + archive/unarchive), SessionsListView (toggle/badge/actions), SettingsView (slider rétention), i18n EN+FR
- tests: retention-settings + session-archive (vitest) + settings-routes étendu ; acceptance-p10.mjs (sweep, event WS, resume d'une session archivée → 201, rétention=0)

packages/server/src/ws/gateway.ts

@@ -13,6 +13,7 @@ import {
 } from '@arboretum/shared';
 import type { ClientBinding, PtyManager } from '../core/pty-manager.js';
 import type { DiscoveryService } from '../core/discovery-service.js';
+import type { SessionArchiveService } from '../core/session-archive.js';
 import type { WorktreeManager } from '../core/worktree-manager.js';
 import type { GroupManager } from '../core/group-manager.js';
 
@@ -27,6 +28,7 @@ export function registerWsGateway(
   app: FastifyInstance,
   manager: PtyManager,
   discovery: DiscoveryService,
+  sessionArchive: SessionArchiveService,
   worktrees: WorktreeManager,
   groups: GroupManager,
   serverVersion: string,
@@ -57,6 +59,10 @@ export function registerWsGateway(
     const onSessionExit = (e: { sessionId: string; exitCode: number | null; signal: number | null }): void => {
       if (subscribedSessions) send({ type: 'session_exit', ...e });
     };
+    // P10 — une session managée vient d'être archivée (auto par ancienneté ou manuellement).
+    const onSessionArchived = (e: { id: string; archivedAt: string }): void => {
+      if (subscribedSessions) send({ type: 'session_archived', sessionId: e.id });
+    };
     // Les sessions découvertes (DiscoveryService) sont relayées sur le même flux que les managées.
     const onDiscoveryUpdate = (session: SessionSummary): void => {
       if (subscribedSessions) send({ type: 'session_update', session });
@@ -85,6 +91,7 @@ export function registerWsGateway(
     };
     manager.on('session_update', onSessionUpdate);
     manager.on('session_exit', onSessionExit);
+    sessionArchive.on('session_archived', onSessionArchived);
     discovery.on('discovery_update', onDiscoveryUpdate);
     worktrees.on('repo_update', onRepoUpdate);
     worktrees.on('repo_removed', onRepoRemoved);
@@ -234,6 +241,7 @@ export function registerWsGateway(
       clearInterval(heartbeat);
       manager.off('session_update', onSessionUpdate);
       manager.off('session_exit', onSessionExit);
+      sessionArchive.off('session_archived', onSessionArchived);
       discovery.off('discovery_update', onDiscoveryUpdate);
       worktrees.off('repo_update', onRepoUpdate);
       worktrees.off('repo_removed', onRepoRemoved);