Show an explicit incomplete-data state when GitHub rate limits

[rho-ricon]

Problem

The GitHub Grid Explorer can appear complete even when GitHub API data is incomplete because the viewer is rate-limited or a fetch partially fails.

For this kind of cockpit UI, incomplete data is risky: a user may browse the grids and make decisions as if all repositories/issues/PRs/workflows were present.

Desired behavior

When the app detects a rate limit or partial data failure:

• show a top-level banner such as GitHub data incomplete;
• mark affected grids/sections with warning badges;
• open a first-detection modal explaining that the current view may be missing data;
• include clear actions:
  • Retry
  • Continue with partial data
  • later, optionally Use a token / sign in

The modal should not be generic error noise. It should protect the user from mistaking partial data for complete data.

Detection notes

Likely signals:

• GitHub API 403 / 429 responses;
• X-RateLimit-Remaining: 0;
• X-RateLimit-Reset for retry timing;
• any fetch group where some resources succeed and others fail.

Acceptance sketch

• Simulate rate-limited API responses in local/mock data.
• Verify the banner and modal appear.
• Verify affected grids are visually marked as incomplete.
• Verify the user can dismiss/continue, but the warning state remains visible.
• Verify successful retry clears the incomplete-data warning.