feat(webui): read-only workflow policy & guardrail visibility (Closes #646)

Phase 3 child of the Web Console epic #631. Operators can now see the active
workflow policy/guardrail configuration from the console instead of reading the
repo tree.

- webui/policy_inventory.py (new): redacted, machine-readable guardrail
  inventory. One row per major guardrail (role separation/RBAC, lease rules,
  worktree binding, merge confirmation, redaction, contamination, allocator
  policy, audit logging, mutation gating) with source pointers (file/module/doc)
  and a compact active projection from the existing safe policy accessors.
  Fail-soft per entry; whole payload run through console_redaction before emit;
  diff vs documented default where feasible.
- webui/policy_views.py (new): HTML cards with source pointers, active config,
  and the documented-default diff; read-only page copy, no forms.
- webui/app.py: register GET /policy and GET /api/v1/policy (additive).
- webui/layout.py: add Policy nav item.
- tests/test_webui_policy_visibility.py (new): guardrail presence + source
  pointers (AC1), redaction incl. planted-secret masking and scan_for_secrets
  (AC2/AC3), read-only page + no-mutation routes (AC4), fail-soft rendering.
- docs/webui-local-dev.md: route table + read-only policy-visibility section.

Read-only throughout; no policy editing, no gate-weakening toggle, secrets
redacted.

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

webui/app.py

@@ -45,6 +45,8 @@ from webui.worktree_scanner import load_hygiene_snapshot, snapshot_to_dict as wo
 from webui.worktree_views import render_worktrees_page
 from webui.runtime_health import load_runtime_snapshot, snapshot_to_dict as runtime_snapshot_to_dict
 from webui.runtime_views import render_runtime_page
+from webui.policy_inventory import load_policy_inventory, snapshot_to_dict as policy_snapshot_to_dict
+from webui.policy_views import render_policy_page
 
 _READ_ONLY_METHODS = frozenset({"GET", "HEAD", "OPTIONS"})
 _AUDIT_MUTATION_PATHS = frozenset({"/audit", "/api/audit"})
@@ -68,6 +70,7 @@ async def home(_request: Request) -> HTMLResponse:
         "<li><strong>Projects</strong> — registry and onboarding (#427)</li>"
         "<li><strong>Prompts</strong> — canonical workflow prompt library (#428)</li>"
         "<li><strong>Runtime</strong> — MCP health and stale-runtime detection (#430)</li>"
+        "<li><strong>Policy</strong> — workflow guardrail configuration visibility (#646)</li>"
         "<li><strong>Audit</strong> — final-report paste and validator preview (#431)</li>"
         "<li><strong>Worktrees</strong> — branch hygiene dashboard (#432)</li>"
         "<li><strong>Leases</strong> — collision and lease visibility (#433)</li>"
@@ -210,6 +213,17 @@ async def api_runtime(_request: Request) -> JSONResponse:
     return JSONResponse(runtime_snapshot_to_dict(load_runtime_snapshot()))
 
 
+async def policy(_request: Request) -> HTMLResponse:
+    snapshot = load_policy_inventory()
+    return HTMLResponse(
+        render_page(title="Policy", body_html=render_policy_page(snapshot))
+    )
+
+
+async def api_v1_policy(_request: Request) -> JSONResponse:
+    return JSONResponse(policy_snapshot_to_dict(load_policy_inventory()))
+
+
 async def _parse_audit_form(request: Request) -> tuple[str, str | None]:
     if request.method == "GET":
         return "", None
@@ -415,6 +429,8 @@ def create_app(*, bind_host: str | None = None) -> Starlette:
             Route("/api/prompts", api_prompts, methods=["GET"]),
             Route("/runtime", runtime, methods=["GET"]),
             Route("/api/runtime", api_runtime, methods=["GET"]),
+            Route("/policy", policy, methods=["GET"]),
+            Route("/api/v1/policy", api_v1_policy, methods=["GET"]),
             Route("/audit", audit, methods=["GET", "POST"]),
             Route("/api/audit", api_audit, methods=["GET", "POST"]),
             Route("/worktrees", worktrees, methods=["GET"]),