v0.2.0

Features

• Add cross-process advisory file locking to FileStorage using std::fs::File::lock / lock_shared for safe concurrent access across OS processes
• Add --data-dir global CLI flag to override the default XDG storage directory

Details

• with_shared_lock allows concurrent readers; with_exclusive_lock provides exclusive writer access
• storage.lock sentinel file is created on construction and preserved across clear_all
• New tests: lockfile_created_on_construction, clear_preserves_lockfile, concurrent_upserts_are_safe