Connect Runta Crew to Cloud Agents and simplify the desktop UI

[shiqimei]

Summary

• replace the local demo path with the concrete Runta Cloud Agents client and device OAuth flow
• align the desktop with the minimal, flat three-column Runta Crew design
• add deterministic generated agent avatars and remove simulated computer UI
• keep credentials and Cloud API requests in the Electron main process
• add managed-provider selection and human account display names
• reconstruct durable conversations from Cloud Agent runs, show user messages immediately, and update running/finished/failed states through polling
• update architecture and API docs to the codex/cloud-agents-v1 contract
• add a real, cleanup-safe Cloud Agents E2E script

Verification

• npm run typecheck
• npm run lint
• npm test -- --run (12 tests)
• npm run build
• npm run package
• npm run smoke

Automatic pull-request CI passed install/typecheck/lint/test/build/package/native-smoke/artifact upload:
https://github.com/runta-dev/runta-crew/actions/runs/32992323857

Cloud Agents E2E

Verified on runta-gcp against the cloud-agents-v1 stack:

• runta_crew device authorization returned 200.
• Authenticated Electron loaded the Shiqi profile and real Agent list.
• The backend E2E passed temporary Agent/runtime creation, workspace operations, a real Kimi run, SSE events, artifact lifecycle, follow-up, cancellation, secondary harness, and cleanup.
• Durable run responses now expose new-run prompts and timestamps while keeping legacy prompt-less runs readable. Backend change: https://github.com/runta-dev/runta/pull/832
• The desktop now renders real historical user/agent turns (for example the Atlas hello turn and its persisted response).

Backend E2E evidence: run 01a03eed-3bf4-7ff2-a6c3-125d94cf731c, session 8f927a17-7107-493b-9b8d-b9ca6ed70e41, follow-up 01a03eed-6610-7c90-bb64-5a15d892de63.