Survive an unwritable state dir (Docker uid-1000 bind mounts)

[AlexNly]

First user report: /newbag fails with the generic error on a fresh Docker install. Root cause: the compose example bind-mounts ./data, Docker creates it root-owned, the container runs as uid 1000 - so the FIRST state write (which /newbag happens to be before any shot) raises PermissionError.

• State degrades to in-memory with one loud, actionable log line instead of raising on every write
• startup probes writability and logs the chown fix immediately
• generic command errors now include the exception summary in the chat reply, so users can self-diagnose
• compose example + README document the chown -R 1000:1000 fix