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

docs/developer-testing-guidelines.md

@@ -54,6 +54,21 @@ Use `-q` for a compact summary and `-v` to see individual test names.
 ./venv/bin/python -m pytest tests/ -q
 ```
 
+### Web UI suite (#436)
+
+Hermetic unittest modules matching `test_webui_*.py` cover route rendering,
+read-only guards, registry/prompt/queue loaders, and optional child-issue
+modules when present on the branch.
+
+```bash
+./scripts/test-webui
+./scripts/ci-webui-check          # skip unless the diff touches web UI paths
+WEBUI_CI_FORCE=1 ./scripts/ci-webui-check
+```
+
+Wire `scripts/ci-webui-check` into Jenkins (or equivalent) for PRs that touch
+`webui/`, `tests/test_webui_*`, or `docs/webui*`.
+
 ### Run targeted tests
 
 ```bash