Feat v0.6.13 responsive spacing

Add spacing token scale (--sp-1 through --sp-12, 4px grid) and tablet
breakpoint (max-width: 1024px). Migrate all kernel CSS and 12 in-tree
extension packages from hardcoded padding/margin/gap to design tokens.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -2,6 +2,36 @@
 
 All notable changes to Armature are documented here.
 
+## v0.6.13 — Responsive & Spacing
+
+Spacing token scale and tablet breakpoint. All kernel CSS and extension
+packages migrated from hardcoded values to design tokens.
+
+### Added
+
+- **Spacing tokens** (`--sp-1` through `--sp-12`) — 4px-grid scale in
+  `variables.css`. Nine stops: 4, 8, 12, 16, 20, 24, 32, 40, 48px.
+  Numeric naming (`--sp-N`), rem-based for zoom/font-size respect.
+- **Tablet breakpoint** (`max-width: 1024px`) — new responsive tier
+  between mobile (768px) and desktop. Secondary workspace pane narrows
+  to 360px, admin sidebar to 120px, settings/admin/editor navs shrink.
+- **Breakpoint documentation** in `EXTENSION-CSS.md` — Mobile (768px),
+  Tablet (1024px), Desktop (default).
+- **Spacing guidelines** in `EXTENSION-CSS.md` — token table with
+  computed pixel values and usage examples.
+
+### Changed
+
+- **8 kernel CSS files** migrated to spacing tokens — `sw-primitives.css`,
+  `modals.css`, `surfaces.css`, `layout.css`, `sw-shell.css`,
+  `primitives.css`, `user-menu.css`, `sw-login.css`. Hardcoded padding,
+  margin, and gap values replaced with `var(--sp-N)`.
+- **12 extension packages** migrated — chat, dashboard, editor,
+  git-board, hello-dashboard, icd-test-runner, notes, schedules,
+  sdk-test-runner, tasks, team-activity-log, workflow-demo.
+- **Login hero breakpoint** normalized from 900px to 1024px (tablet).
+- **Notes mobile breakpoint** normalized from 700px to 768px (standard).
+
 ## v0.6.12 — Extension CSS Isolation
 
 Prefix enforcement prevents extension CSS from leaking into the kernel or