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/tools_intro/__init__.py

@@ -164,10 +164,10 @@ def get_memory_status() -> dict[str, Any]:
         if sem_db.exists():
             conn = sqlite3.connect(str(sem_db))
             row = conn.execute(
-                "SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name='vectors'"
+                "SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name='chunks'"
             ).fetchone()
             if row and row[0]:
-                count = conn.execute("SELECT COUNT(*) FROM vectors").fetchone()
+                count = conn.execute("SELECT COUNT(*) FROM chunks").fetchone()
                 tier3_info["available"] = True
                 tier3_info["vector_count"] = count[0] if count else 0
             conn.close()