feat: implement Hermes session manager with SQLite + JSONL support (Phase 6)

- Add hermes.rs session provider with dual-source scanning:
  SQLite (state.db) as primary, JSONL transcripts as fallback
- Dynamic schema discovery via PRAGMA table_info for SQLite resilience
- Use read_head_tail_lines for efficient JSONL metadata extraction
  (head 30 lines for metadata, tail 10 for last_active_at)
- Support both flat and nested JSONL message formats
- Add SQLite session loading and transactional deletion
- Register hermes in parallel session scan (thread::scope)
- Add "hermes" to frontend ProviderFilter type
- 7 unit tests covering JSONL parsing, SQLite source parsing, deletion

src-tauri/src/session_manager/providers/mod.rs

@@ -1,6 +1,7 @@
 pub mod claude;
 pub mod codex;
 pub mod gemini;
+pub mod hermes;
 pub mod openclaw;
 pub mod opencode;
 mod utils;