@W-22167805@ add sf agent trace list command

[WillieRuemmele]

Work Item

@W-22167805@

Summary

Adds the sf agent trace list command for listing trace files recorded during agent preview sessions. Reads from the local .sfdx/agents/ cache — no org connection required.

Changes

• New command: sf agent trace list
• Flags: --agent (substring match, replaces separate --api-name/--authoring-bundle), --session-id, --since (ISO 8601, validated at flag-parse time)
• Messages: messages/agent.trace.list.md
• Schema and snapshot updated

Files Changed

• src/commands/agent/trace/list.ts
• messages/agent.trace.list.md
• schemas/agent-trace-list.json
• command-snapshot.json
• test/commands/agent/trace/list.test.ts

Test Plan

• 19 unit tests passing
• npm run build and npm test pass cleanly
• Schema and deprecation snapshot regenerated

Dependencies

• Requires agents library PR: @W-22167805@ Add trace session utilities (listSessionTraces, readSessionTrace, readTurnIndex) forcedotcom/agents#273