Keep recent events in telemetry #246

Parent

Agent-side change from the map Agent fleet dashboard: map; the consolidated list is in the resolution of Define the dashboard project. The snapshot shape is decided in Define the telemetry snapshot contract and the command mechanics in Decide the agentctl telemetry command. Terms: Telemetry snapshot and Figure basis in CONTEXT.md; ADR 0006.

What to build

Telemetry includes the agent's most recent events, already redacted, so an operator sees what the agent just did without reading container logs.

Acceptance criteria

• An in-memory ring buffer keeps the last 50 events. It is fed by the JSON event logger after redaction, so every entry has passed through the redactor.
• Entry shape: {timestamp, level, event, issue_number, phase, text}, where text is the event detail truncated to 300 characters.
• limits_checked and tool_call events are excluded.
• recent_events is newest last. The buffer starts empty after a restart.
• Over the snapshot size cap, the oldest events are dropped first.
• Tests: a secret in an event's detail never appears in the snapshot; excluded events are absent; the buffer holds at most 50 entries.

Blocked by

• Serve a telemetry snapshot through agentctl telemetry --json