[codex] Expose chat turn metadata

[realadeel]

Summary

Exposes per-turn chat metadata from agentd and renders it in the web chat UI.

Chat responses now include compact model-call and tool-call metadata while persisted conversation messages remain unchanged.

Impact

• agentd.Chat returns a turn object with model calls, route decisions, token/cost details when present, tool calls, and turn duration.
• Large tool payloads are redacted in metadata.
• The web chat shows collapsible turn details beneath assistant responses.
• Adds tests for inference trace capture and tool metadata redaction.

Validation

• python -m pytest tests/ -q -> 116 passed