[Epic]: make release pipelines more reliable

Library

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Describe the feature that you would like added

At the moment v-build and anyone triggering v9 release is noticed only when it's already too late - broken release 🥲.

We need to improve current situation in 2 areas.

✅ 1. Adding integration tests to make sure following things works:

• we always publish to npm expected assets
  • to mitigate regressions like https://github.com/microsoft/fluentui/pull/27741, https://github.com/microsoft/fluentui/pull/27736, https://github.com/microsoft/fluentui/pull/27745
• custom logic used within release pipelines works
  • to mitigate issues like https://github.com/microsoft/fluentui/pull/27757

✅ 2. Switch to files instead of npmignore

• to mitigate regressions like https://github.com/microsoft/fluentui/pull/27741,
• for rock solid control over what is being shipped ( npmignore and github ignore doesn't work well together )

3. Fallbacks when things out of our control fail:

Npm registry failures:

We need to implement proper fallback behaviours for cases where npm registry errors during npm publish.

This situation puts repo into invalid state, which blocks every contributor. Only remedy ATM is to manually trigger beachball , create PR and merge, which is far from ideal.

We need to implement some graceful fallback mechanism for these situations which is fully automatic.

Have you discussed this feature with our team

v-build

Additional context

No response

Validations

• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

The entry points mentioned are v-build and the v9 release pipelines; no files or tests are named. Start by tracing those pipelines and their npm publish steps, then define integration coverage for published assets and custom release logic, plus automatic fallbacks for npm registry failures.