[RaghavChamadiya]

What

Bare Number#toLocaleString() formats with the runtime's locale, so a server in one locale and a browser in another produced different digit grouping (for example 1,261,599 vs 12,61,599), and hydration failed.

How

• Every bare .toLocaleString() on a number in packages/ui and packages/web now goes through the existing formatNumber, which is pinned to en-US.
• Nullable sites keep undefined.
• Untyped chat tool counts fall back to String(value).

Based on #5058.

Verification

• ui and web tsc --noEmit: clean.
• ui vitest: 3052 tests passing.
• New test forces an en-IN locale and checks that the overview health line and owner labels keep en-US grouping.

[repowise-bot]

Worth a look: 1 thing to check below.

1. 5 files that usually change with this PR's files are not in it: packages/ui/src/refactoring/plan-detail.tsx changed in 15 of the 18 commits that touched packages/ui/src/refactoring/types.ts; packages/ui/src/graph/graph-toolbar.tsx changed in 13 of the 17 commits that touched packages/ui/src/graph/graph-legend.tsx; packages/web/src/app/repos/[id]/refactoring/page.tsx changed in 12 of the 16 commits that touched packages/ui/src/refactoring/refactoring-board.tsx (+2 more)

✅ Health of changed files: 7.1 (unchanged) _{Average full file score (structure and history) of 112 changed code files, weighted by size before this PR; not the repository score.}

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