Add weekly AAT and VRT flaky test reporting

[Copilot]

Adds a read-only script that identifies Playwright tests marked flaky across AAT and VRT workflow runs from the past seven days.

Changelog

New

• Query completed report workflows through the GitHub CLI.
• Parse ANSI-colored Playwright flaky-test summaries.
• Aggregate occurrences into a Markdown report with links to recent runs.
• Support custom repositories, time ranges, and workflow files.

node script/find-flaky-tests.mts --repo primer/react

Changed

• None.

Removed

• None.

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; repository tooling only.

Testing & Reviewing

Review workflow selection, Playwright log parsing, and report aggregation.

[changeset-bot]

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Latest commit: 04a6cd0

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[github-actions]

⚠️ Action required

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Check the integration testing docs for step-by-step instructions. Or, apply the integration-tests: skipped manually label to skip these checks.