feat: Phase 2 Memory Core — structured memory with context integration

Memory Core implementation:
- Memory service with 6 types: identity, preference, project, episodic, knowledge, adaptation
- CRUD operations: create (with dedup), get (filtered), update, invalidate, supersede
- Confidence scoring (0.0-1.0) and lifecycle management (active/superseded/invalid)
- Memory API endpoints: POST/GET/PUT/DELETE /memory

Context builder integration (trust precedence per Master Plan):
  1. Trusted Project State (highest trust, 20% budget)
  2. Identity + Preference memories (10% budget)
  3. Retrieved chunks (remaining budget)

Also fixed database.py to use dynamic settings reference for test isolation.
45/45 tests passing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/atocore/models/database.py

@@ -5,7 +5,7 @@ from contextlib import contextmanager
 from pathlib import Path
 from typing import Generator
 
-from atocore.config import settings
+import atocore.config as _config
 from atocore.observability.logger import get_logger
 
 log = get_logger("database")
@@ -70,7 +70,7 @@ CREATE INDEX IF NOT EXISTS idx_interactions_project ON interactions(project_id);
 
 
 def _ensure_data_dir() -> None:
-    settings.data_dir.mkdir(parents=True, exist_ok=True)
+    _config.settings.data_dir.mkdir(parents=True, exist_ok=True)
 
 
 def init_db() -> None:
@@ -78,14 +78,14 @@ def init_db() -> None:
     _ensure_data_dir()
     with get_connection() as conn:
         conn.executescript(SCHEMA_SQL)
-    log.info("database_initialized", path=str(settings.db_path))
+    log.info("database_initialized", path=str(_config.settings.db_path))
 
 
 @contextmanager
 def get_connection() -> Generator[sqlite3.Connection, None, None]:
     """Get a database connection with row factory."""
     _ensure_data_dir()
-    conn = sqlite3.connect(str(settings.db_path))
+    conn = sqlite3.connect(str(_config.settings.db_path))
     conn.row_factory = sqlite3.Row
     conn.execute("PRAGMA foreign_keys = ON")
     try: