feat(webui): versioned project registry API (Closes #635)

Evolve the MVP project registry (#427) into a versioned, fail-closed
project registry API for the console (Phase 1, read-only).

- Add schema version 2 with project `status`, per-step onboarding
  `state`/`required`, optional redacted `last_seen_health`, and
  `remote_name`. Version 1 files stay loadable and are normalized with
  explicit defaults.
- Serve `/api/v1/projects` and `/api/v1/projects/{project_id}` with API
  provenance (`api_version`, `schema_version`, `source`). `/api/projects`
  is retained as an unversioned Phase 1 alias.
- Replace bare `ValueError` with `RegistryError`, carrying an operator
  `remediation` and `field_path`; invalid registries fail closed as a
  500 JSON payload or a dedicated HTML error page instead of a traceback.
- Reject credential-shaped keys before any DTO is built, reusing
  `registry_safety.is_forbidden_key` as the single source of truth
  shared with the worker registry (#798).
- Render HTML views from `project_to_dict`, so the console and the JSON
  API cannot disagree about status or onboarding progress.
- Document the contract in docs/webui-project-registry-api.md.

Tests: registry load/validate (valid, missing project, schema
validation, credential rejection) and API route coverage.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

docs/webui-local-dev.md

@@ -43,6 +43,10 @@ for the console architecture: layer and authority boundaries, the redaction
 boundary, `/api/v1/...` versioning, the target page map, and the phase gates
 that govern when a write path may open (#632, epic #631).
 
+See [webui-project-registry-api.md](webui-project-registry-api.md) for the
+versioned project registry contract: registry schema versions 1 and 2, project
+status, onboarding checklist state, and the fail-closed error payloads (#635).
+
 ## Routes (MVP)
 
 | Path | Description |
@@ -51,9 +55,11 @@ that govern when a write path may open (#632, epic #631).
 | `/health` | JSON liveness (`status`, `service`, `mode`, `timestamp`) |
 | `/queue` | Live PR and issue queue dashboard (#429) |
 | `/api/queue` | JSON queue export with pagination metadata |
-| `/projects` | Project registry list (#427) |
+| `/projects` | Project registry list with status and onboarding progress (#427, #635) |
 | `/projects/{id}` | Project detail + onboarding checklist |
-| `/api/projects` | JSON registry export |
+| `/api/v1/projects` | Versioned JSON registry export (#635) |
+| `/api/v1/projects/{id}` | Versioned JSON project detail (#635) |
+| `/api/projects` | JSON registry export — unversioned Phase 1 alias of `/api/v1/projects` |
 | `/prompts` | Prompt library with per-prompt copy buttons (#428) |
 | `/api/prompts` | JSON prompt export with workflow hashes |
 | `/runtime` | MCP runtime health and stale detection (#430) |