Starlette 1.3.x prefers httpx2 for starlette.testclient.TestClient; plain
httpx still works but emits StarletteDeprecationWarning.
- Pin httpx2==2.9.1 (keep httpx for MCP/runtime)
- Centralize Web UI TestClient import via tests/webui_testclient.py
- Point all test_webui_* modules at the helper
- Add regression tests that the deprecation warning is gone
Closes#682
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