feat: StreamRow skeleton first paint (Issue #1033)

[VeronicDev]

Summary

Adds a loading skeleton placeholder that renders while StreamRow data is loading, preventing blank flash on first paint (Issue #1033).

Changes

app/components/StreamRow.tsx

• Added loading?: boolean prop to StreamRowProps with JSDoc documentation
• Added early return that renders a themed skeleton placeholder when loading=true (before any hooks, matching StreamProgress pattern)
• Skeleton layout mirrors the real StreamRow:
  • Color stripe placeholder
  • Identity row: circular avatar skeleton + recipient name + schedule text
  • Status badge skeleton
  • Meta section: Rate, Status, Burn-down with dt/dd labels
  • Progress bar skeleton (track + label row)
  • Action button skeleton
• Wrapper carries aria-busy="true" and aria-label="Stream row is loading"
• All skeleton children are aria-hidden="true"
• Respects the density prop: applies stream-row--compact class when density="compact"
• Imports the existing Skeleton component from ./Skeleton

app/components/StreamRow.test.tsx

• Added 12 focused tests under a new loading skeleton (Issue #1033) describe block:
  • Skeleton renders with stream-row--skeleton class
  • aria-busy="true" attribute
  • aria-label="Stream row is loading"
  • No live content (recipient, action button, status badge, progress) leaks
  • Skeleton elements exist
  • Circular avatar skeleton rendered
  • All skeletons have aria-hidden="true"
  • Compact density modifier works with skeleton
  • Color stripe skeleton renders
  • dt elements rendered in meta section
  • Normal render when loading=false
  • Normal render when loading=undefined

Testing

• 89/89 tests pass (all 77 existing + 12 new)
• ESLint clean
• Follows established pattern from StreamProgress skeleton implementation

Closes #1033

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[greatest0fallt1me]

Merged into main via admin resolver (-X theirs).

[greatest0fallt1me]

LGTM — clean, tested. Merged 🙌