fix: enrich OpenCode live status header metadata

[LIU9293]

Summary

• parse OpenCode message.updated info fields into session state by syncing modelID -> model, agent -> agent, and preserving tokens.total in SessionTokenUsage
• update live status title details to render optional metadata in parentheses as available: model, compact token count, agent, non-zero cost, and elapsed time
• add/extend session inspector coverage to verify OpenCode metadata mapping and header rendering behavior (including hiding cost 0)

Testing

• bun test packages/agents/test/session-inspector.test.ts packages/core/test/status-message.test.ts packages/live-status-harness/test/render-status.test.ts
• bun test packages/agents/test/*stream-status.test.ts