feat: add internal web UI server skeleton (Closes #426)

Starlette read-only MVP with shared layout, /health JSON liveness, and
route stubs for projects, prompts, runtime, audit, worktrees, and leases.
Includes scripts/run-webui, docs/webui-local-dev.md, and tests.

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

tests/test_webui_skeleton.py

@@ -0,0 +1,58 @@
+"""Tests for internal web UI skeleton (#426)."""
+import sys
+import unittest
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from starlette.testclient import TestClient
+
+from webui.app import create_app
+
+
+class TestWebuiSkeleton(unittest.TestCase):
+    def setUp(self):
+        self.client = TestClient(create_app())
+
+    def test_health_returns_json(self):
+        response = self.client.get("/health")
+        self.assertEqual(response.status_code, 200)
+        data = response.json()
+        self.assertEqual(data["status"], "ok")
+        self.assertEqual(data["service"], "mcp-control-plane-webui")
+        self.assertEqual(data["mode"], "read-only-mvp")
+        self.assertIn("timestamp", data)
+
+    def test_home_renders(self):
+        response = self.client.get("/")
+        self.assertEqual(response.status_code, 200)
+        self.assertIn("Operator console", response.text)
+        self.assertIn("Read-only MVP", response.text)
+
+    def test_route_stubs_render(self):
+        for path in ("/projects", "/prompts", "/runtime", "/audit"):
+            with self.subTest(path=path):
+                response = self.client.get(path)
+                self.assertEqual(response.status_code, 200)
+                self.assertIn("child issue", response.text.lower())
+
+    def test_extra_stub_routes(self):
+        for path in ("/worktrees", "/leases"):
+            with self.subTest(path=path):
+                self.assertEqual(self.client.get(path).status_code, 200)
+
+    def test_post_is_rejected(self):
+        response = self.client.post("/health")
+        self.assertEqual(response.status_code, 405)
+        self.assertEqual(response.json()["error"], "read-only-mvp")
+
+    def test_nav_links_on_all_pages(self):
+        for path in ("/", "/projects", "/prompts", "/runtime", "/audit"):
+            with self.subTest(path=path):
+                text = self.client.get(path).text
+                for href in ("/projects", "/prompts", "/runtime", "/audit"):
+                    self.assertIn(f'href="{href}"', text)
+
+
+if __name__ == "__main__":
+    unittest.main()