fix(worktree): audit observation fetch/display for composite project names

Three sites didn't account for parent/worktree composite naming:

- PaginationHelper.stripProjectPath: marker used full composite, breaking
  path sanitization for worktrees checked out outside a parent/leaf layout.
  Now extracts the leaf segment.
- observations/store.ts: fallback imported getCurrentProjectName from
  shared/paths.ts (a duplicate impl without worktree detection). Switched
  to getProjectContext().primary so writes key into the same project as
  reads.
- SearchManager.getRecentContext: fallback used basename(cwd) and lost
  the parent prefix, making the MCP tool find nothing in worktrees.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/services/worker/SearchManager.ts

@@ -13,7 +13,6 @@
  * - TimelineBuilder: Timeline construction
  */
 
-import { basename } from 'path';
 import { SessionSearch } from '../sqlite/SessionSearch.js';
 import { SessionStore } from '../sqlite/SessionStore.js';
 import { ChromaSync } from '../sync/ChromaSync.js';
@@ -22,6 +21,7 @@ import { TimelineService } from './TimelineService.js';
 import type { TimelineItem } from './TimelineService.js';
 import type { ObservationSearchResult, SessionSummarySearchResult, UserPromptSearchResult } from '../sqlite/types.js';
 import { logger } from '../../utils/logger.js';
+import { getProjectContext } from '../../utils/project-name.js';
 import { formatDate, formatTime, formatDateTime, extractFirstFile, groupByDate, estimateTokens } from '../../shared/timeline-formatting.js';
 import { ModeManager } from '../domain/ModeManager.js';
 
@@ -1319,7 +1319,7 @@ export class SearchManager {
    * Tool handler: get_recent_context
    */
   async getRecentContext(args: any): Promise<any> {
-    const project = args.project || basename(process.cwd());
+    const project = args.project || getProjectContext(process.cwd()).primary;
     const limit = args.limit || 3;
 
     const sessions = this.sessionStore.getRecentSessionsWithStatus(project, limit);