feat: per-role agent assignment (Design, QA, Architect, etc.) + bug: OpenCode worker delegates to Codex exhausting quota #6917

Feature Request: Per-Role Agent Assignment

Currently AO assigns a single worker agent per session. In real workflows, different roles need different specialized agents:

Proposed: Allow project/session config to map roles → agents:

# .ao/config.yaml or project config
agents:
  design: opencode-v2
  qa: opencode-v2
  architect: opencode-v2
  implementation: kilocode
  review: codex

Orchestrator would spawn the correct agent when a task with that role is queued.

Bug: OpenCode Worker Delegates to Codex (Quota Exhaustion)

Environment:

• AO version: 0.14.2
• Project: registered with ao project add
• Worker agent configured: opencode-v2 (via --worker-agent opencode-v2 or project config)
• Actual behavior: Tasks delegated to Codex, hitting 5-hour rate limit

Expected: When worker agent is opencode-v2, the spawned session should run OpenCode, not Codex.

Observed:

• ao agent ls shows opencode-v2: authorized
• Spawn command: ao spawn --project test --worker-agent opencode-v2 --name "feat-xyz"
• Session starts but actual work done by Codex (visible in token usage / model name)
• Codex free tier quota exhausted in < 1 hour

Suspected causes:

1. Harness resolution falling back to Codex when OpenCode server not ready
2. --worker-agent ignored, defaulting to project orchestrator.agent or global default
3. Agent switch happening mid-session without user consent

Logs to check: ao hooks output, session agent_switches table, daemon logs.

Impact

• Cannot use OpenCode for implementation (main use case)
• Forced to wait 5 hours for Codex quota reset
• No way to assign specialized agents per role

Suggested Priority

1. Bug fix (P0): Ensure --worker-agent / project config is respected
2. Per-role agent config (P1): Enable multi-agent workflows