docs(flaky-tests): changelog for failure details and copy prompt in browser extension

[samgutentag]

Summary

Adds a changelog entry for the new failure details section in the Trunk browser extension's test-results panel. When Trunk detects test failures, users can now expand a section to see per-test name, file, error snippet, prev/next failure navigation, and a Copy Prompt button that copies an AI investigation prompt to the clipboard.

Changes:

• Added changelog/2026-06-17-flaky-tests-browser-extension-failure-details.mdx
• Updated docs.json nav to include the new entry in June 2026

Note: This PR is a changelog entry only. A merge-queue/browser-extensions.mdx prose section update should be coordinated with PR #245 (which also modifies that file). The browser-extensions.mdx update for failure details should be folded into or stacked on top of #245.

Source

• trunk2 PR: https://github.com/trunk-io/trunk2/pull/4209

Test plan

• Check Mintlify preview link (posted on the PR by the Mintlify GitHub app)

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Project	Status	Preview	Updated (UTC)
trunk	🟢 Ready	View Preview	Jun 17, 2026, 12:14 PM

[samgutentag]

Verification status (June 17, 2026): pending

The eng PR is merged, but the failure-details UI is gated by an in-extension storage feature flag (isBrowserExtensionFeatureEnabledInStorage("testDetails")) and was noted as having a DONOTLAND marker in the render layer for design polish. The feature is not yet enabled for end users in production.

• Eng PR: https://github.com/trunk-io/trunk2/pull/4209
• Flag: testDetails (in-extension storage flag, not LaunchDarkly)
• Flag state: LD not consulted; inferred from fallback signals -- isBrowserExtensionFeatureEnabledInStorage("testDetails") gates the GET_PR_TEST_FAILURE_DETAILS handler in background.ts; PR description notes render layer has a DONOTLAND marker for design polish
• Signals:
  • Eng PR #4209 merged 2026-06-16 into trunk-io/trunk2 main
  • Feature gated behind isBrowserExtensionFeatureEnabledInStorage("testDetails") -- returns FEATURE_DISABLED when off
  • PR description explicitly states: "Failure-details UI is functional but marked DONOTLAND in render -- design polish still needed"
  • No LaunchDarkly flag found in the diff; gate is extension-internal storage flag

Hold this docs PR as draft until the DONOTLAND marker is removed from the render layer and the testDetails storage flag is enabled for production users.

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