fix(cli): exempt backend command from DB migration gate

`backend setup/status/teardown` manage host prerequisites only and never
open the store, but the CLI dispatcher ran the schema-migration gate before
every command. On a non-TTY runner the gate's `Migrate now? [y/N]` prompt
reads EOF and refuses, so `backend status --backend=firecracker` exits 1 —
breaking the Firecracker CI preflight on any host without a pre-migrated DB.

Exempt `backend` from the gate; store-touching commands stay gated.

Fixes #419

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1qRZTJC6qgBsUSjNrBdkX

bot_bottle/cli/__init__.py

@@ -38,6 +38,13 @@ COMMANDS = {
     "supervise": cmd_supervise,
 }
 
+# Commands that manage host prerequisites (or are otherwise store-free) and
+# must run before — or without — a migrated DB. `backend` provisions/probes
+# the host (TAP pool, /dev/kvm, firecracker) and never opens the store, so
+# gating it on the schema breaks preflight on a fresh CI runner where stdin
+# isn't a TTY and the migration prompt can't be answered.
+NO_MIGRATION_COMMANDS = frozenset({"backend"})
+
 
 def usage() -> None:
     sys.stderr.write(f"usage: {PROG} <command> [args...]\n\n")
@@ -80,7 +87,7 @@ def main(argv: list[str] | None = None) -> int:
         usage()
         die(f"unknown command: {command}")
     mgr = StoreManager.instance()
-    if not mgr.is_migrated():
+    if command not in NO_MIGRATION_COMMANDS and not mgr.is_migrated():
         sys.stderr.write("bot-bottle: database schema is out of date\n")
         sys.stderr.write("Migrate now? [y/N] ")
         sys.stderr.flush()

tests/unit/test_cli_dispatch.py

@@ -95,5 +95,60 @@ class TestMainDispatch(unittest.TestCase):
             self.assertEqual(130, main(["x"]))
 
 
+class TestMigrationGate(unittest.TestCase):
+    """The dispatcher's schema-migration gate (cli/__init__.py)."""
+
+    def setUp(self) -> None:
+        # Force the "schema out of date" branch for every test here.
+        patcher = patch.object(StoreManager, "is_migrated", return_value=False)
+        patcher.start()
+        self.addCleanup(patcher.stop)
+        self.addCleanup(StoreManager.reset)
+
+    def test_store_command_blocks_when_stdin_cannot_confirm(self) -> None:
+        # Non-TTY stdin at EOF (as in CI): the [y/N] prompt reads "" and the
+        # command is refused rather than migrating silently.
+        ran: list[bool] = []
+
+        def handler(_rest: list[str]) -> int:
+            ran.append(True)
+            return 0
+
+        with patch.dict(climod.COMMANDS, {"list": handler}), \
+                patch("sys.stdin", io.StringIO("")), \
+                patch("sys.stderr", io.StringIO()):
+            self.assertEqual(1, main(["list"]))
+        self.assertEqual([], ran, "gated command must not dispatch")
+
+    def test_backend_command_skips_gate(self) -> None:
+        # `backend` provisions/probes the host and never opens the store, so
+        # it must run even on an unmigrated DB with unanswerable stdin.
+        ran: list[bool] = []
+
+        def handler(_rest: list[str]) -> int:
+            ran.append(True)
+            return 0
+
+        with patch.dict(climod.COMMANDS, {"backend": handler}), \
+                patch("sys.stdin", io.StringIO("")), \
+                patch("sys.stderr", io.StringIO()):
+            self.assertEqual(0, main(["backend", "status"]))
+        self.assertEqual([True], ran, "exempt command must dispatch")
+
+    def test_store_command_migrates_on_confirmation(self) -> None:
+        migrated: list[bool] = []
+
+        def handler(_rest: list[str]) -> int:
+            return 0
+
+        with patch.dict(climod.COMMANDS, {"list": handler}), \
+                patch.object(StoreManager, "migrate",
+                             side_effect=lambda: migrated.append(True)), \
+                patch("sys.stdin", io.StringIO("y\n")), \
+                patch("sys.stderr", io.StringIO()):
+            self.assertEqual(0, main(["list"]))
+        self.assertEqual([True], migrated, "confirmed gate must migrate")
+
+
 if __name__ == "__main__":
     unittest.main()