refactor: format diff line counts through one shared helper

[maria-rcks]

Diff line counts were formatted ad hoc at each call site, and most rendered raw integers, so large changes read as +85000 -30000. Diff count formatting now lives in one shared helper, formatDiffCount in @t3tools/client-runtime/diff-count. It applies the viewer's locale grouping (+85,000 -30,000) through a single cached Intl.NumberFormat.

Call sites now using it:

• web: thread details Changes row, commit dialog file list and selected totals, sidebar row diff, item inspector, PR diff stat (previously its own toLocaleString())
• mobile: review sheet file rows and header summary, commit sheet, activity inspector

The diff viewer file headers come from @pierre/diffs, which can't import app code, so the existing patch for that package formats its two header counts the same way.

Display components are unchanged. They still differ in color, minus sign, and order, and merging them would be a separate design decision. The compact DiffStatLabel (83.1k) is also unchanged. The native iOS/Android review diff file headers still print raw counts; that needs a native rebuild and is left for a follow-up.

Verified in a local dev web client: the thread details Changes row and the diff panel file header render grouped counts for 85,000/30,000 and 2,400/1,500 line working tree diffs (before, the header rendered -1500 +2400). Mobile sites were not run on a device.

Written by claude-opus-5-5 in T3 Code (Claude Code harness).

[macroscopeapp]

Approvability

Verdict: Approved at 8877bed

Macroscope's review found this PR approvable — This is a contained presentation refactor that consistently groups existing diff line counts across web, mobile, and diff-viewer surfaces. It introduces no new workflow, schema, configuration default, deployment behavior, or static-analysis suppression.

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📥 Commits

Reviewing files that changed from the base of the PR and between 0d12db6 and 8877bed.

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📒 Files selected for processing (10)

• apps/mobile/src/features/review/ReviewSheet.tsx
• apps/mobile/src/features/review/useReviewDiffData.ts
• apps/mobile/src/features/threads/git/GitCommitSheet.tsx
• apps/mobile/src/lib/threadActivityInspector.ts
• apps/web/src/components/GitActionsControl.tsx
• apps/web/src/components/Sidebar.tsx
• apps/web/src/components/chat/V2ItemInspector.tsx
• apps/web/src/components/pullRequest/pullRequestPresentation.tsx
• packages/client-runtime/package.json
• packages/client-runtime/src/diffCount.ts

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🚧 Files skipped from review as they are similar to previous changes (5)

• apps/web/src/components/chat/V2ItemInspector.tsx
• apps/mobile/src/features/review/useReviewDiffData.ts
• apps/mobile/src/features/review/ReviewSheet.tsx
• apps/web/src/components/GitActionsControl.tsx
• apps/mobile/src/lib/threadActivityInspector.ts

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📝 Walkthrough

📝 Walkthrough

Walkthrough

Mobile and web diff displays now format addition and deletion counts with a shared locale-aware formatter. The patched diff viewer adds search and related editor updates.

Changes

Diff Review and Search

Layer / File(s)	Summary
Shared diff count formatter packages/client-runtime/src/diffCount.ts, packages/client-runtime/package.json	The client runtime adds and exports formatDiffCount, which applies locale-aware digit grouping.
Mobile diff count displays apps/mobile/src/features/review/ReviewSheet.tsx, apps/mobile/src/features/review/useReviewDiffData.ts, apps/mobile/src/features/threads/git/GitCommitSheet.tsx, apps/mobile/src/lib/threadActivityInspector.ts, apps/web/src/components/GitActionsControl.test.ts	Mobile review, commit, activity, and checkpoint counts use the shared formatter. A test mock now includes insertion and deletion counts.
Web and patched diff displays apps/web/src/components/GitActionsControl.tsx, apps/web/src/components/Sidebar.tsx, apps/web/src/components/chat/V2ItemInspector.tsx, apps/web/src/components/pullRequest/pullRequestPresentation.tsx, patches/@pierre%2Fdiffs@1.5.2.patch	Web displays use the shared formatter. The patch adds diff search and related virtualized layout updates, and formats file-header counts.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: juliusmarminge

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Merge Risk: ⚪ Minimal · up to 8877b

Diff counts remain readable with locale grouping, and folded-file search can expand a matching file before navigating. The earlier web test fixture now includes its count values, leaving no identified merge-blocking risk.

Architecture Summary

Architecture risk: 🔵 Low · up to 0d12d

The change affects 3 systems.

Changed systems: apps/mobile, apps/web, patches

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — apps/mobile (service) was modified; 4 changed files map to changed impact.
• observed — apps/web (ui) was modified; 4 changed files map to changed impact.
• observed — patches (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in apps/mobile/src/features/review/ReviewSheet.tsx: Addition and deletion counts in ReviewFileNavigatorRow are now locale-formatted before display; previously they were rendered as unformatted numbers.
• observed — Modified behavior in apps/mobile/src/features/review/useReviewDiffData.ts: formatHeaderDiffSummary now applies toLocaleString() to file totals and parsed-diff totals before adding the existing + and - prefixes.
• observed — Modified behavior in apps/mobile/src/features/threads/git/GitCommitSheet.tsx: The selected-file insertion and deletion totals now use locale-aware formatting instead of displaying raw numbers.
• observed — Modified behavior in apps/mobile/src/features/threads/git/GitCommitSheet.tsx: Insertion and deletion counts in the file preview now use locale-aware formatting instead of raw numbers.

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Pre-merge checks | 3 | 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check		The description explains the problem, implementation, affected areas, verification results, limitations, screenshots, and agent details. It does not provide the required issue or maintainer approval l…	Add the triaged bug issue or maintainer approval discussion with the approval comment. If no prior issue or discussion is required, explain why this focused fix is an obvious bug that qualifies for the exemption.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title clearly and concisely describes the main change: using one shared helper to format diff line counts.

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Full details: Description check

Explanation

The description explains the problem, implementation, affected areas, verification results, limitations, screenshots, and agent details. It does not provide the required issue or maintainer approval link, or explain why this focused fix qualifies for an exemption.

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Actionable comments posted: 1

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Inline comments:
Review comments at @apps/web/src/components/GitActionsControl.tsx:
- Line 2028: Update the status fixtures used by GitActionsControl tests to
provide numeric insertion and deletion counts, so formatting file.insertions and
file.deletions cannot receive undefined; normalize missing counts in the
rendering path only if the status contract permits them.

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 5f7294d and e2a31e5.

📒 Files selected for processing (7)

• apps/mobile/src/features/review/ReviewSheet.tsx
• apps/mobile/src/features/review/useReviewDiffData.ts
• apps/mobile/src/features/threads/git/GitCommitSheet.tsx
• apps/mobile/src/lib/threadActivityInspector.ts
• apps/web/src/components/GitActionsControl.tsx
• apps/web/src/components/Sidebar.tsx
• apps/web/src/components/chat/V2ItemInspector.tsx

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