feat: Distinguish empty-state messages in PullRequestsTab

[ObaHacker]

Summary

Implemented the empty-state split in the Pull Requests tab and added comprehensive test coverage for each state.

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Changes

src/features/maintainers/components/pull-requests/PullRequestsTab.tsx

• Added explicit empty-state branching for:
  • No repositories selected.
  • Selected repositories with no pull requests.
  • Filters/search returning no matches.
• Marked empty-state messaging as an announced status region using role="status".
• Kept Clear filters available in the no-matches state.
• Added TSDoc documentation around the empty-state decision logic.
• Tightened React hook dependency handling.

src/features/maintainers/components/pull-requests/PullRequestsTab.test.tsx

• Added test coverage for:
  • No repositories selected state.
  • No pull requests state.
  • No matching results state.
  • Filtered-empty-to-results transition.

vite.config.ts

• Updated configuration to support the new test coverage requirements.

vitest.config.ts

• Updated Vitest configuration.

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Verification

Passed

• npx eslint src/features/maintainers/components/pull-requests/PullRequestsTab.tsx src/features/maintainers/components/pull-requests/PullRequestsTab.test.tsx
• git diff --check

Known Issues

• npm run typecheck

Type checking is currently failing due to unrelated pre-existing issues in:

• src/shared/components/SearchModal.tsx
• src/shared/utils/focusTrap.ts

Test Execution

• Full Vitest run

Unable to complete an end-to-end Vitest run in the current environment because the config loader fails while resolving vitest.config.ts with:

Cannot read directory "../..": Access is denied

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Security Impact

• Presentation-only change.
• No authentication logic modified.
• No persistence layer changes.
• No data validation changes.
• No new security surface introduced.

closes #81

[Jagadeeshftw]

distinguishing the empty-state messages in the pull requests tab is a nice ux detail, much clearer than a single generic message. rebased on latest main, merged. thanks!