feat(web/ui): consolidate dialogs, cards, and breakpoints (Pass 3)

- Unify modal/dialog system; .modal-* are now aliases of .dialog-*
- Migrate WorkspacesPage, start-tool-modal, merge-dialog, workspace-tools-panel to .dialog-*
- Add .card-sm/.card-md/.card-lg/.card-elevated/.card-borderless modifiers
- Apply card utilities across workspaces, projects, ssh-keys, workspace-detail, git-history
- Remove duplicated card-like background/border/padding from page CSS
- Remove 860px breakpoint; standardize on 767px/768px mobile split
- Add docs/development/ui-review-checklist.md
- Archive web-ui-spacing-typography-rework OpenSpec change

docs/development/ui-review-checklist.md

@@ -0,0 +1,14 @@
+# UI Change Review Checklist
+
+When changing styles or components in `apps/web/src`:
+
+- [ ] New layout/spacing uses `--space-*` tokens, not hardcoded px/rem.
+- [ ] New type sizes use `--font-size-*` tokens.
+- [ ] New radii use `--radius-*` tokens.
+- [ ] New shadows use `--shadow-*` tokens.
+- [ ] No new inline `style={{...}}` blocks for static layout (computed values are OK).
+- [ ] Interactive controls meet `min-height: var(--touch-target)`.
+- [ ] `:focus-visible` states are visible and use `--brand`.
+- [ ] Mobile layouts are tested down to 375px wide.
+- [ ] New class names are defined in a stylesheet before being referenced.
+- [ ] Breakpoints use the literal values from `tokens.css` (`480px`, `768px`, `1024px`, `1280px`).