feat: add persistent memory system + SQLite session store

Two-part implementation:

Part A - Curated Bounded Memory:
- New memory tool (tools/memory_tool.py) with MEMORY.md + USER.md stores
- Character-limited (2200/1375 chars), § delimited entries
- Frozen snapshot injected into system prompt at session start
- Model manages pruning via replace/remove with substring matching
- Usage indicator shown in system prompt header

Part B - SQLite Session Store:
- New hermes_state.py with SessionDB class, FTS5 full-text search
- Gateway session.py rewritten to dual-write SQLite + legacy JSONL
- Compression-triggered session splitting with parent_session_id chains
- New session_search tool with Gemini Flash summarization of matched sessions
- CLI session lifecycle (create on launch, close on exit)

Also:
- System prompt now cached per session, only rebuilt on compression
  (fixes prefix cache invalidation from date/time changes every turn)
- Config version bumped to 3, hermes doctor checks for new artifacts
- Disabled in batch_runner and RL environments

cli.py

@@ -723,6 +723,14 @@ class HermesCLI:
         if self.agent is not None:
             return True
         
+        # Initialize SQLite session store for CLI sessions
+        self._session_db = None
+        try:
+            from hermes_state import SessionDB
+            self._session_db = SessionDB()
+        except Exception:
+            pass  # SQLite session store is optional
+        
         try:
             self.agent = AIAgent(
                 model=self.model,
@@ -735,6 +743,7 @@ class HermesCLI:
                 ephemeral_system_prompt=self.system_prompt if self.system_prompt else None,
                 session_id=self.session_id,  # Pass CLI's session ID to agent
                 platform="cli",  # CLI interface — agent uses terminal-friendly formatting
+                session_db=self._session_db,
             )
             return True
         except Exception as e:
@@ -1775,6 +1784,12 @@ class HermesCLI:
             pass
         finally:
             self._should_exit = True
+            # Close session in SQLite
+            if hasattr(self, '_session_db') and self._session_db and self.agent:
+                try:
+                    self._session_db.end_session(self.agent.session_id, "cli_close")
+                except Exception:
+                    pass
             _run_cleanup()
             print("\nGoodbye! ⚕")