fix: Discord memory bug — add session continuity + 6 memory system fixes (#147)

Discord created a new agent per message with no conversation history,
causing Timmy to lose context between messages (the "yes" bug). Now uses
a singleton agent with per-channel/thread session_id, matching the
dashboard's session.py pattern. Also applies _clean_response() to strip
hallucinated tool-call JSON from Discord output.

Additional fixes:
- get_system_context() no longer clears the handoff file (was destroying
  session context on every agent creation)
- Orchestrator uses HotMemory.read() to auto-create MEMORY.md if missing
- vector_store DB_PATH anchored to __file__ instead of relative CWD
- brain/schema.py: removed invalid .load dot-commands from INIT_SQL
- tools_intro: fixed wrong table name 'vectors' → 'chunks' in tier3 check

Co-authored-by: Trip T <trip@local>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/timmy/memory/vector_store.py

@@ -12,7 +12,7 @@ from datetime import datetime, timezone
 from pathlib import Path
 from typing import Optional
 
-DB_PATH = Path("data/swarm.db")
+DB_PATH = Path(__file__).parent.parent.parent.parent / "data" / "swarm.db"
 
 # Simple embedding function using sentence-transformers if available,
 # otherwise fall back to keyword-based "pseudo-embeddings"