fix: address CodeRabbit review — remove side-effectful test import and normalize timeline depth params

- tests/servers/mcp-tool-schemas.test.ts: remove `import '../../src/servers/mcp-server.js'`
  which triggered server startup side effects; test only needs to read the TS source as text
- src/services/worker/SearchManager.ts: add Number() coercion for depth_before/depth_after
  in timeline(), getContextTimeline(), getTimelineByQuery() — HTTP query strings deliver
  these as strings, coercion ensures they are always numbers before being passed to
  filterByDepth() and getTimelineAround*()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/servers/mcp-tool-schemas.test.ts

@@ -6,10 +6,7 @@
  */
 import { describe, it, expect } from 'bun:test';
 
-// Import the tools array directly — static schema validation, no server needed
-import '../../src/servers/mcp-server.js';
-
-// Re-import via dynamic require to access the tools array
+// Static schema validation — reads source as text, no server startup needed
 const mcpServerPath = new URL('../../src/servers/mcp-server.ts', import.meta.url).pathname;
 
 describe('MCP tool inputSchema declarations', () => {