feat(webui): evolve application shell for Phase 1 console IA (Closes #638)

Introduce a single nav-config module (webui/nav.py) driving grouped
navigation across the epic #631 Phase 1 information architecture:
Health, Traffic, Runtime/Sessions, Projects, Inventory, Timeline,
Policy (placeholder), and Insights (placeholder). The shell header now
carries a read-only environment badge (local/remote from WEBUI_HOST), a
mode: read-only badge, and a Docs link. Home summarizes the console
purpose, lists the Phase 1 surfaces by group, and links the MVP legacy
pages.

Not-yet-implemented surfaces (/sessions, /inventory, /timeline,
/policy, /insights) resolve to graceful read-only stub pages rather than
404s; their backing views land in later child issues of #631 (inventory
surfaces backed by #636). Mutating methods on stub routes still fail
closed with read-only-mvp. No privileged action controls are added.

Adds tests/test_webui_shell.py covering nav groups, badge presence,
environment classification, docs link, stub routes (200 + read-only),
and home content. Updates docs/webui-local-dev.md with the new routes
and a Phase 1 shell section.

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

webui/app.py

@@ -11,6 +11,7 @@ from starlette.routing import Route
 
 from webui.deployment_boundary import deployment_snapshot
 from webui.layout import render_page
+from webui.nav import NAV_GROUPS, STUB_PAGES
 from webui.project_registry import find_project, load_registry, registry_to_dict
 from webui.project_views import render_project_detail, render_projects_list
 from webui.prompt_library import find_prompt, library_to_dict
@@ -43,24 +44,62 @@ def _stub_page(title: str, description: str) -> HTMLResponse:
     return HTMLResponse(render_page(title=title, body_html=body))
 
 
+_LEGACY_PAGES = (
+    ("/queue", "Queue", "live PR and issue dashboard (#429)"),
+    ("/projects", "Projects", "registry and onboarding (#427)"),
+    ("/prompts", "Prompts", "canonical workflow prompt library (#428)"),
+    ("/runtime", "Runtime", "MCP health and stale-runtime detection (#430)"),
+    ("/audit", "Audit", "final-report paste and validator preview (#431)"),
+    ("/worktrees", "Worktrees", "branch hygiene dashboard (#432)"),
+    ("/leases", "Leases", "collision and lease visibility (#433)"),
+    ("/actions", "Actions", "gated write-action framework (#434)"),
+)
+
+
+def _render_home_nav_groups() -> str:
+    groups = []
+    for group in NAV_GROUPS:
+        items = "".join(
+            f'<li><a href="{item.href}">{item.label}</a>'
+            + ("" if item.status == "live" else " <span class=\"muted\">(stub)</span>")
+            + "</li>"
+            for item in group.items
+        )
+        groups.append(f"<h3>{group.label}</h3><ul>{items}</ul>")
+    return "".join(groups)
+
+
 async def home(_request: Request) -> HTMLResponse:
+    legacy = "".join(
+        f"<li><strong>{label}</strong> — {desc} "
+        f'(<a href="{href}">{href}</a>)</li>'
+        for href, label, desc in _LEGACY_PAGES
+    )
     body = (
         "<h2>Operator console</h2>"
-        "<p>Local entry point for MCP Control Plane operational views.</p>"
-        "<ul>"
-        "<li><strong>Queue</strong> — live PR and issue dashboard (#429)</li>"
-        "<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>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>"
-        "<li><strong>Actions</strong> — gated write-action framework (#434)</li>"
-        "</ul>"
+        "<p>Read-only home for the MCP Control Plane Phase 1 operator console. "
+        "Gitea, MCP capability gates, and canonical workflows remain the source "
+        "of truth; this console never mutates them.</p>"
+        "<h2>Phase 1 surfaces</h2>"
+        + _render_home_nav_groups()
+        + "<h2>MVP legacy pages</h2>"
+        "<ul>" + legacy + "</ul>"
     )
     return HTMLResponse(render_page(title="Home", body_html=body))
 
 
+async def phase_stub(request: Request) -> HTMLResponse:
+    """Graceful read-only placeholder for a not-yet-implemented Phase 1 surface."""
+    title, description = STUB_PAGES[request.url.path]
+    body = (
+        f"<h2>{title}</h2>"
+        f'<div class="stub"><p>{description}</p>'
+        "<p>Phase 1 shell placeholder — no write actions. Tracked under "
+        "epic #631.</p></div>"
+    )
+    return HTMLResponse(render_page(title=title, body_html=body))
+
+
 async def health(_request: Request) -> JSONResponse:
     bind_host = _request.app.state.webui_bind_host
     return JSONResponse({
@@ -291,6 +330,10 @@ def create_app(*, bind_host: str | None = None) -> Starlette:
                 methods=["POST"],
             ),
             Route("/api/leases", api_leases, methods=["GET"]),
+            *[
+                Route(path, phase_stub, methods=["GET"])
+                for path in STUB_PAGES
+            ],
         ],
         exception_handlers={405: method_not_allowed},
     )