feat(web): choose the default diff file state

[maria-rcks]

Diff files always opened expanded. Settings → General now lets you choose Expanded or Collapsed as the default for the diff view and pull requests' Code tab on web and desktop. Expanded remains the default for existing settings; individual file toggles, expand/collapse all, and file-tree reveal keep working.

Verified against real working-tree changes and GitHub PR #11480 through the web client and server, including reopening, persistence across reloads, both choices, individual toggles, and file-tree reveal. Inspected settings in light/dark themes at 1280px and 800px. Blacksmith passed contracts/web/desktop typechecks, scoped lint, and existing settings, persistence, diff folding, file-tree, and viewer tests. Native desktop launch and mobile are unverified; mobile's separate diff viewer is outside this change.

The recordings below use animated GIFs for inline GitHub playback.

Model: gpt-6-astra. Harness: Codex.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR adds a persisted user-facing setting that controls whether production diff and pull-request Code views open with files expanded or collapsed, wiring the choice through settings, contracts, and renderers. Because it changes product defaults, the change warrants human review.

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[coderabbitai]

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ℹ️ Recent review info

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Plan: Advanced

Run ID: 0d1d91c2-9568-4d92-9958-39e7a96b549c

📥 Commits

Reviewing files that changed from the base of the PR and between 8ddd9f7 and d953233.

📒 Files selected for processing (9)

• apps/desktop/src/settings/DesktopClientSettings.test.ts
• apps/web/src/clientPersistenceStorage.test.ts
• apps/web/src/components/DiffPanel.tsx
• apps/web/src/components/pullRequest/PullRequestCodeTab.tsx
• apps/web/src/components/pullRequest/pullRequestDiff.logic.ts
• apps/web/src/components/settings/SettingsPanels.tsx
• apps/web/src/components/settings/settingsSearch.ts
• packages/contracts/src/settings.test.ts
• packages/contracts/src/settings.ts

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📝 Walkthrough

Walkthrough

The change adds a persisted diffFilesCollapsed client setting. The settings UI exposes and searches this preference. Diff panels and pull request code views use it as the default when no file-specific override exists. Tests cover schema handling and persistence.

Changes

Default diff file state

Layer / File(s)	Summary
Settings contract and persistence packages/contracts/src/settings.ts, packages/contracts/src/settings.test.ts, apps/web/src/clientPersistenceStorage.test.ts, apps/desktop/src/settings/DesktopClientSettings.test.ts	The client settings schema, patch schema, persistence tests, and desktop fixture support diffFilesCollapsed, which defaults to false.
Settings UI and reset behavior apps/web/src/components/settings/SettingsPanels.tsx, apps/web/src/components/settings/settingsSearch.ts	General settings exposes Expanded and Collapsed options, reset behavior, changed-setting tracking, and search terms for the new preference.
Diff collapse state application apps/web/src/components/DiffPanel.tsx, apps/web/src/components/pullRequest/PullRequestCodeTab.tsx, apps/web/src/components/pullRequest/pullRequestDiff.logic.ts	Diff views use the saved preference when no fold override exists. Callback and memo dependencies include the preference, and the state documentation describes the caller-supplied default.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant SettingsPanels
  participant ClientSettings
  participant PullRequestCodeTab
  participant DiffPanel

  SettingsPanels->>ClientSettings: update diffFilesCollapsed
  ClientSettings-->>PullRequestCodeTab: provide saved setting
  ClientSettings-->>DiffPanel: provide saved setting
  PullRequestCodeTab->>PullRequestCodeTab: apply setting when no fold override exists
  DiffPanel->>DiffPanel: seed collapsed file state from setting

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Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to d9532

The new default diff-file state is persisted and applied consistently to working-tree and pull-request diffs, with existing interaction behavior retained.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 9 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The description clearly explains the change, verification scope, UI impact, screenshots, recordings, and unverified areas. It does not use the template headings or include the checklist, but the requi…
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a selectable default diff file state.

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