ci(e2e): keep Playwright traces and outputs from bazel-remote-gates as a run artifact

[Jesssullivan]

First bounded PR from the QA LOOK-loop design (2026-08-28): the blog's e2e already runs remotely on the overlay dind pool inside bazel-remote-gates, but a failure leaves no evidence — PLAYWRIGHT_TRACE_MODE defaulted to off and the job had zero upload-artifact steps (the one in ci.yml belongs to Lighthouse in build-and-test). Today's 1/330 e2e timeout on #263 could only be read from stdout.

• .bazelrc: test --test_env=PLAYWRIGHT_TRACE_MODE (alongside the existing Chromium env passthrough).
• playwright.bazel.config.ts: outputDir = $TEST_UNDECLARED_OUTPUTS_DIR/playwright under bazel test (falls back to test-results), so traces/screenshots/error-contexts survive the sandbox in bazel-testlogs/playwright_chromium_e2e/test.outputs/outputs.zip.
• ci.yml gates job: PLAYWRIGHT_TRACE_MODE: retain-on-failure; an if: always() step copies bazel-testlogs/playwright_chromium_e2e (dereferenced, zip expanded) into artifacts/playwright-e2e, then actions/upload-artifact@v7 (SHA-pinned) uploads it, 7-day retention, if-no-files-found: warn.

No new permissions or secrets; nothing about what is tested changes. Local: node scripts/test-workflow-authority.mjs green (file reads only). Hosted CI is the proof — the artifact should appear on this PR's own gates run.

[Jesssullivan]

Scope note against TIN-3130 / R336 (GF is retiring mandatory GitHub-Actions-artifact evidence latches because retention quota can block publishers): this upload is evidence, not a latch — no job, gate, or publisher consumes it, if-no-files-found: warn, 7-day retention on a personal-account public repo. Written exit per R336: when the gf-qa-look RustFS bucket + its write identity exist (GF #1668 design), the Upload e2e evidence step is replaced by the bucket upload in the same job; the Bazel-side change (undeclared outputs + trace mode) is venue-independent and stays.

[Jesssullivan]

Run 33203042020 proved the plumbing (the failing spec's trace.zip and error-context.md were retained under test.outputs/playwright/…) and then Bazel refused the test: output tree artifact playwright_chromium_e2e/test.outputs was not created. Bazel 8 keeps undeclared outputs as an unzipped tree artifact by default; the Playwright spec directory names are non-ASCII (search-Search-—-color-mode-…). HEAD adds test --zip_undeclared_test_outputs so it is a single outputs.zip (the evidence step already unzips it).

Note for the record: this is the second 30 s locator.evaluate timeout today in e2e/search.spec.ts › color mode … in light and dark modes (also #263's first gates run) — that is an intermittent, not a one-off; its trace will now be attached.