feat: add a live maintainer public-safe PR preview simulator wired to settings-preview

[Crystora]

Summary

• Adds a live maintainer public-safe PR preview simulator for issue feat(control-panel): add public-safe preview simulator #135, wired to the existing settings-preview API.

Closes: #135

Scope

• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked an issue, or this is small enough that the summary explains why an issue is not needed.

Validation

• git diff --check
• npm run actionlint
• npm run typecheck
• npm run test:coverage locally; global coverage stays at or above 97% for lines, statements, functions, and branches
• npm run test:workers
• npm run build:mcp
• npm run test:mcp-pack
• npm run ui:openapi:check
• npm run ui:lint
• npm run ui:typecheck
• npm run ui:build
• npm audit --audit-level=moderate
• New or changed behavior has unit/integration tests for new branches, fallback paths, and sanitizer boundaries

If any required check was skipped, explain why:

• None. Full npm run test:ci passed.

Safety

• No secrets, wallet details, hotkeys, coldkeys, user PATs, private keys, raw trust scores, private rankings, or private maintainer evidence are exposed.
• Public GitHub text stays sanitized, low-noise, and does not imply compensation guarantees or optimization tactics.
• Auth, cookie, CORS, GitHub App, Cloudflare, or session changes include negative-path tests.
• API/OpenAPI/MCP behavior is updated and tested where needed.
• UI changes use live API data or real empty/error/loading states, not production mock/demo fallbacks.
• Visible UI changes include screenshots or a short recording.
• Public docs/changelogs are updated where needed; changelogs are only edited for release-prep PRs.

Notes

• The UI now posts sample scenarios to the existing dry-run endpoint and renders the returned decision, warnings, actions, and sanitized public comment preview.

[JSONbored]

@bittoby this looks good.

A few notes:

• The simulator calls the existing settings-preview endpoint instead of hardcoding policy results.
• The form helper tests cover repo parsing, labels, linked issues, and scenario payload construction.
• The UI keeps the public-safe preview boundary visible without adding a fake data path.
• No code changes requested.

Validation expected:

• Current GitHub checks are green.