[upstream #17138] #17138: Empty Playwright shard plan fails the mock e2e job #389

Raised by a local cross-family review on LibreChat-AI#17138 (local:921fbe9:L-001) and LibreChat-AI#17141 (local:907b2a0:L-001). Neither PR touches CI; the review range included dev's own changes. Pre-existing on dev since LibreChat-AI#17019.

When graduated-spec skipping (repo var CODEGRAPH_E2E_SKIP=on) leaves fewer spec files than shards, or the reservation leaves a shard empty, .github/scripts/playwright-shards.mjs plan writes an empty shard-tests.txt and only prints a warning. .github/workflows/playwright-mock.yml then runs npx playwright test --test-list=e2e/.generated/shard-tests.txt, which fails with "No tests found" and blocks the required e2e gate even though the selected suite passed.

Suggested fix: skip the Playwright invocation for an empty plan (or pass --pass-with-no-tests only when the plan is empty), keeping the failure for an empty suite listing, and cover the empty-shard execution path in the script's tests. The skip path is dark until the repo var is turned on upstream, so this is not P1.