feat: add StoreManager singleton for centralized store migration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bot_bottle/store_manager.py

@@ -0,0 +1,60 @@
+"""Singleton manager for all bot-bottle SQLite stores (PRD 0013)."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+try:
+    from .audit_store import AuditStore
+    from .queue_store import QueueStore
+except ImportError:
+    from audit_store import AuditStore  # type: ignore[import-not-found]  # pylint: disable=import-error,no-name-in-module
+    from queue_store import QueueStore  # type: ignore[import-not-found]  # pylint: disable=import-error,no-name-in-module
+
+_instance: StoreManager | None = None
+
+
+class StoreManager:
+    """Owns db_path and delegates migrate/check_migrations across all stores.
+
+    Use instance() for normal access. Call reset(db_path) in tests to swap
+    the singleton to a temp path, then reset() with no args to restore the
+    default."""
+
+    def __init__(self, db_path: Path | None = None) -> None:
+        if db_path is None:
+            # Lazy import to avoid a circular dependency: supervise imports
+            # StoreManager at module level; StoreManager must not import
+            # supervise at module level in return.
+            try:
+                from .supervise import host_db_path
+            except ImportError:
+                from supervise import host_db_path  # type: ignore[import-not-found]  # pylint: disable=import-error,no-name-in-module
+            db_path = host_db_path()
+        self.db_path = db_path
+
+    @classmethod
+    def instance(cls) -> StoreManager:
+        global _instance
+        if _instance is None:
+            _instance = cls()
+        return _instance
+
+    @classmethod
+    def reset(cls, db_path: Path | None = None) -> None:
+        """Replace the singleton. Pass db_path for test isolation; omit to restore default."""
+        global _instance
+        _instance = cls(db_path)
+
+    def check_migrations(self) -> bool:
+        return (
+            QueueStore("", self.db_path).check_migrations()
+            and AuditStore(self.db_path).check_migrations()
+        )
+
+    def migrate(self) -> None:
+        QueueStore("", self.db_path).migrate()
+        AuditStore(self.db_path).migrate()
+
+
+__all__ = ["StoreManager"]