feat: stabilize scheduler control flow with commit gate and writeback retry

[treeson-li]

What

• add unified scheduler commit gate with lease owner + version checks
• enforce state action allowlist and cooldown guards
• separate writeback retry chain from execution redispatch
• add scheduler baseline/replay scripts and gate tests
• update frontend scheduler panel + API typing
• add TemplatePanel support for 御前议政 + 自由下旨
• upgrade 御前议政 to a dedicated discussion window with round-robin speaking, final decision, and explicit outcomes:
  • handoff to Taizi for execution
  • terminate topic when not suitable
• update architecture doc and rebuild dashboard dist assets
• ignore local .helloagents/ artifacts

Commit breakdown

1. feat(scheduler): backend + scripts + tests
2. feat(frontend): api + task modal
3. docs: architecture update
4. build(dashboard): dist artifacts
5. feat(template): add court discuss + free edict
6. chore(git): ignore local planning artifacts
7. feat(court): backend handoff/terminate workflow + tests
8. feat(template): court discuss window + round-robin decision flow
9. build(dashboard): dist artifacts for window flow

Validation

• python -m py_compile dashboard/server.py
• pytest -q (28 passed)
• cd edict/frontend && npm run build