Ports 16 diverged Playwright e2e specs verbatim from langgraph-python
and adds 3 previously-missing specs (chat-customization-css,
prebuilt-sidebar, reasoning-custom). All 19 files are byte-identical
to LGP, mirroring the same approach the recent ADK parity push used
for the demo pages.
Why this matters even though D5 is the gold standard: the per-package
Playwright suites (`pnpm test:e2e`) are the local dev validation loop.
Without parity here, a contributor editing google-adk's CopilotChat
surface has no local check that matches what langgraph-python ships,
and tiny divergences between the two surfaces (missing testids, stale
selectors, wrong assertion shapes) silently accumulate until they
surface as D5 regressions in CI.
Alem Tuzlak
02e48162c4