[Quality audit] Reduce frontend, store, and shared-lib duplication

[johannesjo]

Derived from the local audit report CODE_QUALITY_FINDINGS.md created on 2026-05-30.

Scope

This issue groups renderer, store, and shared-library simplification opportunities.

Findings

• Finding 6: shortcut matching is duplicated and semantically inconsistent.
  • Evidence: src/lib/shortcuts.ts, src/lib/keybindings/match.ts, src/lib/keybindings/resolve.ts.
  • Fix direction: store app shortcuts as KeyBinding-shaped records and share modifier normalization/matching.
• Finding 20: prompt detection is duplicated between main and renderer.
  • Evidence: electron/mcp/prompt-detect.ts, src/store/taskStatus.ts.
  • Fix direction: move shared prompt detection to an importable pure helper.
• Finding 21: diff review duplicates ReviewProvider state and flow.
  • Evidence: src/components/ReviewProvider.tsx, src/components/ScrollingDiffView.tsx.
  • Fix direction: route diff selection through a shared provider/hook path.
• Finding 22: ScrollingDiffView has two hidden-context implementations.
  • Evidence: GapView and TrailingGap duplicate content fetching, context construction, highlighting, rendering, and expansion.
  • Fix direction: extract a shared context-line loader/expander.
• Finding 23: SettingsDialog theme grids are duplicated.
  • Fix direction: extract ThemeGrid(slot), PresetThemeCard, and CustomThemeCard.
• Finding 24: SettingsDialog repeats checkbox/card setting rows.
  • Fix direction: extract SettingsCheckboxRow and a small SettingsSection wrapper.
• Finding 25: Sidebar repeats task row chrome.
  • Fix direction: extract TaskRowShell, DirectBranchBadge, and shared attention/focus style helpers.
• Finding 26: NewTaskDialog carries reusable option UI inline.
  • Fix direction: extract CheckboxOption, InlineBanner, DockerTaskOptions, and CoordinatorTaskOptions.
• Finding 27: task/agent record construction is duplicated in store.
  • Fix direction: extract createAgentRecord(...) and base task builders.
• Finding 28: task deletion and active-neighbor selection are duplicated.
  • Fix direction: extract pure draft cleanup primitives and neighbor-selection helpers while preserving lifecycle differences.
• Finding 29: base64 terminal decoding is duplicated.
  • Fix direction: move decoder to a shared utility used by desktop and remote terminal views.
• Finding 31: keybinding override resolution is duplicated.
  • Fix direction: extract resolveOneBinding; keep exports focused on inclusion of unbound rows.
• Finding 32: light terminal theme palette is copied twice.
  • Fix direction: extract LIGHT_TERMINAL_THEME.
• Finding 33: custom theme parsing/validation repeats primitives.
  • Fix direction: extract isHexTerminalBackground, collectAllowedVars, and formatVarLines while preserving current validation behavior unless intentionally changed.
• Finding 34: Electron window wrapper retains no-op compatibility methods.
  • Fix direction: remove no-op methods and call-site awaits/catches if no supported platform behavior remains.

Acceptance checks

• affected component tests
• store tests
• keybinding and custom-theme tests
• npm run typecheck
• focused browser/UI smoke checks for touched flows