feat: Release v4.0.0 - Plugin data directory and auto-starting worker

BREAKING CHANGES:
- Data directory moved from ~/.claude-mem/ to ${CLAUDE_PLUGIN_ROOT}/data/
- Fresh start required - no migration from v3.x databases
- Worker service now auto-starts on SessionStart hook

New Features:
- MCP Search Server with 6 specialized search tools
- FTS5 full-text search across observations and sessions
- Auto-starting worker service in SessionStart hook
- Citation support for search results (claude-mem:// URIs)

Changes:
- Updated paths.ts to use CLAUDE_PLUGIN_ROOT for data directory
- Added worker auto-start logic to context hook
- Updated worker service to write port file to plugin data dir
- Bumped version to 4.0.0 in package.json and plugin.json
- Created comprehensive CHANGELOG.md documenting v4.0.0 changes
- Updated README.md with v4.0.0 breaking changes and features
- Rebuilt all hooks and worker service

Technical Improvements:
- Improved error handling and graceful degradation
- Structured logging across all components
- Enhanced plugin integration with Claude Code

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/hooks/new.ts

@@ -1,6 +1,7 @@
 import path from 'path';
 import { SessionStore } from '../services/sqlite/SessionStore.js';
 import { createHookResponse } from './hook-response.js';
+import { getWorkerPortFilePath } from '../shared/paths.js';
 
 export interface UserPromptSubmitInput {
   session_id: string;
@@ -14,10 +15,8 @@ export interface UserPromptSubmitInput {
  */
 async function getWorkerPort(): Promise<number | null> {
   const { readFileSync, existsSync } = await import('fs');
-  const { join } = await import('path');
-  const { homedir } = await import('os');
 
-  const portFile = join(homedir(), '.claude-mem', 'worker.port');
+  const portFile = getWorkerPortFilePath();
 
   if (!existsSync(portFile)) {
     return null;