Run Operator ambient loop

[edwin-zvs]

Summary

• Add an idle ambient loop for the daemon-owned Operator/orchestrator zarvis session.
• Inject bounded synthetic OBSERVATION: ambient operator loop tick turns so the Operator can quietly inspect state, update widgets, notify, or reply noted.
• Keep ambient ticks advisory: they use normal zarvis turn/tool/approval machinery and suppress visible minibuffer chatter when the model merely responds.
• Document the behavior in specs/0020-operator-runs-ambiently.md.

Testing

• cargo check -p agentd-adapter-zarvis
• cargo test -p agentd-adapter-zarvis observe
• cargo build

Notes

This PR touches crates/adapter-zarvis, so the relevant binary is agentd-adapter-zarvis.