docs: update reorganize-long-files spec to include CSS reorganization

Add Phase 2 (CSS Reorganization) covering:
- Restore styles/ directory (tokens, global, utilities, syntax-highlight)
- Restore styles/pages/*.css for page-specific styles
- Restore 11 component CSS modules from monolithic styles.css
- Delete styles.css after extraction

Shift frontend page extraction phases to 3-7.
Add visual regression checks to integration phase.

Quality gates unchanged: tsc, build, py_compile, file size limits

openspec/changes/reorganize-long-files/spec.md

@@ -47,7 +47,40 @@ Split the following pages into a thin page shell + extracted components:
 - Extract `ProjectEditDialog` → edit form in dialog
 - Page becomes: data loader + layout + dialog state manager
 
-#### 2. Backend Router Slimming
+#### 2. CSS Reorganization
+
+**`styles.css` (5,683 lines → deleted)**
+- Restore `styles/` directory with extracted files:
+  - `styles/tokens.css` — CSS custom properties (colors, spacing, typography)
+  - `styles/global.css` — global reset, body, shell layout
+  - `styles/utilities.css` — utility classes (.stack, .card, .muted, etc.)
+  - `styles/syntax-highlight.css` — code highlighting
+- Restore `styles/pages/*.css` — page-specific styles:
+  - `styles/pages/dashboard.css`
+  - `styles/pages/projects.css`
+  - `styles/pages/sessions.css`
+  - `styles/pages/settings.css`
+  - `styles/pages/ssh-keys.css`
+  - `styles/pages/git-history.css`
+  - `styles/pages/repo-workspace.css`
+- Restore component CSS modules:
+  - `components/features/terminal/TerminalComponent.module.css`
+  - `components/features/git/GitToolbar.module.css`
+  - `components/features/git/CommitDialog.module.css`
+  - `components/features/git/MergeDialog.module.css`
+  - `components/features/git/FileEditor.module.css`
+  - `components/features/git/FileBrowser.module.css`
+  - `components/features/git/FileViewer.module.css`
+  - `components/features/git/CommitPanel.module.css`
+  - `components/features/session/InstanceList.module.css`
+  - `components/features/settings/SettingsTabLayout.module.css`
+  - `components/layout/AppShell.module.css`
+- Update all component imports to use `import styles from './ComponentName.module.css'`
+- Update `main.tsx` to import `styles/tokens.css`, `styles/global.css`, `styles/utilities.css`, `styles/syntax-highlight.css`
+- Update each page to import its `styles/pages/*.css`
+- Delete monolithic `styles.css`
+
+#### 3. Backend Router Slimming
 
 **`api/tool/tool_instances.py` (2,900 → ~300 lines)**
 - Extract terminal WebSocket handlers → `api/tool/terminal.py` (~400 lines)
@@ -72,19 +105,20 @@ Split the following pages into a thin page shell + extracted components:
 - Frontend UI behavior changes (same components, same interactions)
 - Moving existing `features/` components (already organized)
 - Renaming files (naming already done)
-- CSS changes (styles already work)
+- Changing any CSS rules (only moving them)
 
 ## Acceptance Criteria
 
 1. All pages ≤ 150 lines (except `RepoWorkspacePage` which may stay at ~150)
 2. All API routers ≤ 400 lines
-3. All existing tests pass without modification (behavior unchanged)
-4. All existing API endpoints return identical responses
-5. Frontend `npm run typecheck` passes
-6. Frontend `npm run build` passes
-7. Backend `py_compile` passes on all files
-8. No import errors in browser console
-9. File count increases (more files, smaller files)
+3. No monolithic `styles.css` — all CSS in `styles/` directory or `.module.css` files
+4. All existing tests pass without modification (behavior unchanged)
+5. All existing API endpoints return identical responses
+6. Frontend `npm run typecheck` passes
+7. Frontend `npm run build` passes
+8. Backend `py_compile` passes on all files
+9. No import errors in browser console
+10. File count increases (more files, smaller files)
 
 ## Preconditions