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/services/worker-service.ts

@@ -12,6 +12,7 @@ import { parseObservations, parseSummary } from '../sdk/parser.js';
 import type { SDKSession } from '../sdk/prompts.js';
 import { findAvailablePort } from '../utils/port-allocator.js';
 import { logger } from '../utils/logger.js';
+import { getWorkerPortFilePath, ensureAllDataDirs } from '../shared/paths.js';
 
 const MODEL = 'claude-sonnet-4-5';
 const DISALLOWED_TOOLS = ['Glob', 'Grep', 'ListMcpResourcesTool', 'WebSearch'];
@@ -91,10 +92,10 @@ class WorkerService {
 
         // Write port to file for hooks to discover
         const { writeFileSync } = require('fs');
-        const { join } = require('path');
-        const { homedir } = require('os');
-        const portFile = join(homedir(), '.claude-mem', 'worker.port');
+        ensureAllDataDirs(); // Ensure data directory exists
+        const portFile = getWorkerPortFilePath();
         writeFileSync(portFile, port.toString(), 'utf8');
+        logger.info('SYSTEM', `Port file written to ${portFile}`);
 
         resolve();
       }).on('error', reject);