feat(webui): test coverage and CI gate (#436)

Add consolidated MVP route/read-only tests, path-filter helpers, and
scripts/test-webui plus scripts/ci-webui-check for Jenkins path-filtered
runs on PRs touching web UI surfaces.

Closes #436

tests/test_webui_ci_gate.py

@@ -0,0 +1,54 @@
+"""Tests for web UI CI path-filter gate (#436)."""
+import os
+import subprocess
+import sys
+import unittest
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from webui.ci_paths import should_run_webui_ci, touches_webui_surface
+
+_REPO_ROOT = Path(__file__).resolve().parent.parent
+
+
+class TestCiPathMatching(unittest.TestCase):
+    def test_positive_paths(self):
+        for path in (
+            "webui/app.py",
+            "tests/test_webui_skeleton.py",
+            "docs/webui-local-dev.md",
+            "scripts/test-webui",
+        ):
+            with self.subTest(path=path):
+                self.assertTrue(touches_webui_surface(path))
+
+    def test_negative_paths(self):
+        for path in ("mcp_server.py", "tests/test_mcp_server.py", "README.md"):
+            with self.subTest(path=path):
+                self.assertFalse(touches_webui_surface(path))
+
+    def test_should_run_aggregate(self):
+        self.assertTrue(should_run_webui_ci(["README.md", "webui/layout.py"]))
+        self.assertFalse(should_run_webui_ci(["mcp_server.py", "gitea_auth.py"]))
+
+
+class TestCiRunnerScript(unittest.TestCase):
+    def test_test_webui_smoke(self):
+        script = _REPO_ROOT / "scripts" / "test-webui"
+        result = subprocess.run(
+            ["bash", str(script), "-q"],
+            cwd=_REPO_ROOT,
+            capture_output=True,
+            text=True,
+            timeout=60,
+            env={
+                **os.environ,
+                "WEBUI_TEST_PATTERN": "test_webui_skeleton.py",
+            },
+        )
+        self.assertEqual(result.returncode, 0, result.stderr or result.stdout)
+
+
+if __name__ == "__main__":
+    unittest.main()