fix: make orchestrator teardown timeout configurable (closes #435)

Resolves via ENV VAR -> orchestrator DB config -> default (30 s, up from 5 s):
  BOT_BOTTLE_ORCHESTRATOR_TEARDOWN_TIMEOUT_SECONDS
  teardown_timeout_seconds key in new orchestrator_config table (bot-bottle.db)

New OrchestratorConfigStore (same DbStore/TableMigrations pattern as the
registry) stores the DB-level setting. resolve_teardown_timeout() implements
the priority chain and is called at stack.callback registration time in all
three backends (macos_container, docker, firecracker).

bot_bottle/orchestrator/config_store.py

@@ -0,0 +1,112 @@
+"""Per-host orchestrator configuration store (key/value settings in bot-bottle.db).
+
+Co-tenants the shared `bot-bottle.db` via the `DbStore` framework.  Settings
+are readable by the host launch path directly (no HTTP round-trip to the
+orchestrator), so they take effect even before the orchestrator is reachable.
+"""
+
+from __future__ import annotations
+
+import os
+import sqlite3
+from pathlib import Path
+
+from ..db_store import DbStore
+from ..migrations import TableMigrations
+from ..paths import host_db_path
+
+TEARDOWN_TIMEOUT_KEY = "teardown_timeout_seconds"
+TEARDOWN_TIMEOUT_ENV = "BOT_BOTTLE_ORCHESTRATOR_TEARDOWN_TIMEOUT_SECONDS"
+DEFAULT_TEARDOWN_TIMEOUT_SECONDS = 30.0
+
+_MIGRATIONS = TableMigrations(
+    "orchestrator_config",
+    [
+        """
+        CREATE TABLE IF NOT EXISTS orchestrator_config (
+            key   TEXT PRIMARY KEY,
+            value TEXT NOT NULL
+        )
+        """,
+    ],
+)
+
+
+class OrchestratorConfigStore(DbStore):
+    """Key/value store for orchestrator settings in the shared host DB."""
+
+    def __init__(self, db_path: Path | None = None) -> None:
+        super().__init__(db_path or host_db_path(), _MIGRATIONS)
+
+    def _connect(self) -> sqlite3.Connection:
+        conn = super()._connect()
+        conn.execute("PRAGMA busy_timeout=5000")
+        return conn
+
+    def get(self, key: str) -> str | None:
+        """Return the value for `key`, or None if absent."""
+        try:
+            with self._connection() as conn:
+                row = conn.execute(
+                    "SELECT value FROM orchestrator_config WHERE key = ?", (key,)
+                ).fetchone()
+        except sqlite3.OperationalError:
+            return None
+        return row["value"] if row else None
+
+    def set(self, key: str, value: str) -> None:
+        """Upsert a setting."""
+        with self._connection() as conn:
+            conn.execute(
+                "INSERT OR REPLACE INTO orchestrator_config (key, value) VALUES (?, ?)",
+                (key, value),
+            )
+        self._chmod()
+
+    def delete(self, key: str) -> bool:
+        """Remove a setting. Returns True if the key existed."""
+        with self._connection() as conn:
+            cur = conn.execute(
+                "DELETE FROM orchestrator_config WHERE key = ?", (key,)
+            )
+        return cur.rowcount > 0
+
+
+def resolve_teardown_timeout(db_path: Path | None = None) -> float:
+    """Return the teardown timeout to use, in priority order:
+
+    1. ``BOT_BOTTLE_ORCHESTRATOR_TEARDOWN_TIMEOUT_SECONDS`` env var
+    2. ``teardown_timeout_seconds`` key in the orchestrator config DB
+    3. ``DEFAULT_TEARDOWN_TIMEOUT_SECONDS`` (30 s)
+    """
+    raw = os.environ.get(TEARDOWN_TIMEOUT_ENV, "").strip()
+    if raw:
+        try:
+            value = float(raw)
+            if value > 0:
+                return value
+        except ValueError:
+            pass
+
+    store = OrchestratorConfigStore(db_path)
+    if not store.is_migrated():
+        store.migrate()
+    raw_db = store.get(TEARDOWN_TIMEOUT_KEY)
+    if raw_db is not None:
+        try:
+            value = float(raw_db)
+            if value > 0:
+                return value
+        except ValueError:
+            pass
+
+    return DEFAULT_TEARDOWN_TIMEOUT_SECONDS
+
+
+__all__ = [
+    "OrchestratorConfigStore",
+    "resolve_teardown_timeout",
+    "TEARDOWN_TIMEOUT_KEY",
+    "TEARDOWN_TIMEOUT_ENV",
+    "DEFAULT_TEARDOWN_TIMEOUT_SECONDS",
+]