docs: add "Working with the agent" (norms for reading and instructing inferencebot)

A first draft of the member-facing norms listed as a design goal on
co-op/support#17: where the agent speaks and listens, what to ask it for,
what not to ask it in a shared room, what it does without confirmation,
what always needs a human, and how it is stopped. Linked from the README
index and the Matrix section of getting-started. Nothing here changes how
the agent is configured.

README.md

@@ -16,6 +16,7 @@ funded through our [Open Collective](https://opencollective.com/inference-cooper
 - **Want API access?** → [API access](api-access.md) — use our models programmatically.
 - **Want community chat?** → [Getting started · Matrix](getting-started.md) — our federated Matrix server, including how to connect from any client and how to use an existing Matrix account.
 - **Curious how it works?** → [Infrastructure](infrastructure.md) — a map of the stack and the codebase.
+- **Wondering about the bot?** → [Working with the agent](working-with-the-agent.md) — what inferencebot does, who can instruct it, and what always needs a human.
 - **Need help or have an idea?** → [Support & feature requests](https://git.inference.coop/co-op/support) — open an issue.
 
 ## Key links