ci: establish native Playwright baseline

[ostenbom]

What does this PR do?

Establish the unchanged native Playwright baseline for the Endform comparison in this fork. This is an empty commit: product code, test assertions, browser installation, retry policy, fixture setup, and eight-shard distribution are unchanged.

Selected benchmark: the main Chromium product suite on both Node and Cloudflare. The existing full CI plan also schedules its supplemental jobs; those remain intact. The completed baseline is passing: https://github.com/endformdev/emdash/actions/runs/37708672502, tested commit 40152078f550ba50e012812450f175799d88db43.

Type of change

• Bug fix
• Feature (requires maintainer-approved Discussion)
• Refactor (no behavior change)
• Translation
• Documentation
• Performance improvement
• Tests
• Chore (dependencies, CI, tooling)

Checklist

• I have read CONTRIBUTING.md
• pnpm typecheck passes
• pnpm lint passes
• pnpm test passes (or targeted tests for my change)
• pnpm format has been run
• I have added/updated tests for my changes (if applicable)
• User-visible strings in the admin UI are wrapped for translation (if applicable). Do not include messages.po changes except in translation PRs — a workflow extracts catalogs on merge to main.
• I have added and reviewed the user-facing changeset (if this PR changes a published package)
• New features link to an approved Discussion: https://github.com/emdash-cms/emdash/discussions/...
• I have included screenshots below if this PR changes the UI

AI-generated code disclosure

• This PR includes AI-generated code — model/tool: GPT-6 / Codex (CI coordination; no code changes)

Screenshots / test output

Not applicable: no UI, localization, published-package, feature, or test-body changes, so screenshots, changeset, Discussion, and new regression tests are unnecessary. The baseline changes no files. The full CI workflow passed, including typecheck, lint, package tests, browser tests, and all eight product E2E shards.

Measured sample: one completed native CI run. Main product suite: 362 Chromium tests selected on each target; Node 328 passed / 34 skipped, Cloudflare 315 passed / 47 skipped (existing gates). CI retries remain 1, with one worker per shard. The eight shards run Node then Cloudflare. No test failures or flaky-result summaries were reported.

Timing: whole CI workflow 19m 58s; product test-stage wall-clock span 16m 49s, including global setup/startup within the test commands and gaps between Node and Cloudflare. Node test-command durations range 2m 49s–7m 30s; Cloudflare 2m 35s–8m 37s. Summed test-command runner time is 78m 47s; it is not the wall-clock runtime. Shard jobs began 23–24s after workflow creation. Dependency installation took 31–36s per shard and combined fixture builds took 1m 23s–2m 3s. Runners: existing GitHub-hosted ubuntu-latest; all browser-install steps retained.

Fork-specific setup: GitHub required initial workflow activation before it registered workflows. No product, assertion, fixture, or workflow changes were needed for the native run.