Prevent repeated PR list skeleton shifts

[rrbe]

Summary

• reserve each Branch and PR Diff skeleton only once per rendered DOM row
• remove empty info rows after skeleton cleanup so the document-start CSS keeps row height reserved
• skip title-link nodes during skeleton reservation
• reuse the already-loaded token for the Branch GraphQL batch

Root cause

The 2-second navigation fallback reruns skeleton reservation. When an async feature returned no data, its skeleton was cleared, then recreated and cleared again on every poll. The empty info-row also remained mounted, hiding the CSS height reservation and allowing the row to shrink between passes.

Verification

• pnpm test (32 files, 227 tests)
• pnpm typecheck
• pnpm build
• git diff --check