fix(reporters): keep the watch banner red while other files fail

[nundorn]

Fixes #10695.

On a rerun the banner reports PASS while the summary directly above it counts a failure:

 Test Files  1 failed | 1 passed (2)
      Tests  1 failed | 1 passed (2)

 PASS  Waiting for file changes...

onWatcherStart only receives the files from the run that just finished, so hasFailed(files) cannot see files that failed earlier and were not rerun. reportTestSummary already folds them in via failedUnwatchedFiles, which is why only the banner disagreed.

reporter-failed.test.ts already covered this scenario but waited for Waiting for file changes..., which is the PASS banner, so the old behaviour was pinned by the suite. That wait now expects the FAIL banner, and a second case covers fixing the failing file so the banner cannot get stuck red.

The discussion on #10695 also explored a separate PREVIOUS FAILS section. This PR does not attempt that.

Written by an AI agent (Claude Code) on behalf of @nundorn, who reviewed it before it was posted.

[github-actions]

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[sheremet-va]

Ask your code assistant to read AGENTS.md

[github-actions]

Hello @nundorn. Your PR has been labeled maybe automated because it appears to have been fully generated by AI with no human involvement.

To keep your PR open, please follow these steps:

• Confirm that you are a real human. If you are an automated agent, disclose that
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Please, do not generate or format the response with AI. If you do not speak English, reply in your native language or use translation software like Google Translate or Deepl. If the response is generated, the PR will be closed automatically.

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[sheremet-va]

Doesn't seem like you've read the comments in the issue. Please don't waste maintainers time