Initial import of Shirobana bot backend

Include utility modules, shared channels, prompts, read-only skills, wardrobe memory and regression tests. Externalize legacy credentials and exclude private runtime state.

bot-utility/agent/__init__.py

@@ -0,0 +1,22 @@
+"""Agent tool runtime for the utility bot.
+
+The package deliberately does not import legacy handlers at module import time.
+This keeps mode storage and artifact management usable without optional bot
+dependencies and avoids starting background services during tool discovery.
+"""
+
+from .artifacts import ArtifactError, ArtifactStore
+from .capture import CaptureChannel
+from .executor import ToolExecutor
+from .models import ToolContext, ToolResult
+from .modes import ModeStore
+
+__all__ = [
+    "ArtifactError",
+    "ArtifactStore",
+    "CaptureChannel",
+    "ModeStore",
+    "ToolContext",
+    "ToolExecutor",
+    "ToolResult",
+]