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/shared/paths.ts

@@ -7,10 +7,23 @@ import { fileURLToPath } from 'url';
 /**
  * Simple path configuration for claude-mem
  * Standard paths based on Claude Code conventions
+ *
+ * v4.0.0: Data directory now uses CLAUDE_PLUGIN_ROOT when available
  */
 
 // Base directories
-export const DATA_DIR = process.env.CLAUDE_MEM_DATA_DIR || join(homedir(), '.claude-mem');
+// Priority: CLAUDE_PLUGIN_ROOT/data > CLAUDE_MEM_DATA_DIR > ~/.claude-mem
+const getDataDir = (): string => {
+  if (process.env.CLAUDE_PLUGIN_ROOT) {
+    return join(process.env.CLAUDE_PLUGIN_ROOT, 'data');
+  }
+  if (process.env.CLAUDE_MEM_DATA_DIR) {
+    return process.env.CLAUDE_MEM_DATA_DIR;
+  }
+  return join(homedir(), '.claude-mem');
+};
+
+export const DATA_DIR = getDataDir();
 export const CLAUDE_CONFIG_DIR = process.env.CLAUDE_CONFIG_DIR || join(homedir(), '.claude');
 
 // Data subdirectories
@@ -40,6 +53,13 @@ export function getWorkerSocketPath(sessionId: number): string {
   return join(DATA_DIR, `worker-${sessionId}.sock`);
 }
 
+/**
+ * Get worker port file path
+ */
+export function getWorkerPortFilePath(): string {
+  return join(DATA_DIR, 'worker.port');
+}
+
 /**
  * Ensure a directory exists
  */