feat: add OpenSpec specs and changes for ASW restructure

Specs: repo-structure, 10 framework layer specs, packs, site.
Changes: repo-restructure (10 tasks), css-refactor (12 tasks),
legacy-import (proposal + triage categories).

Supersede docs/css-refactor-plan.md in favor of OpenSpec change.

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

openspec/specs/framework/utilities/spec.md

@@ -0,0 +1,27 @@
+# Spec: Utilities (Layer 08)
+
+File: `src/layers/08-utilities.css`
+
+## Purpose
+
+Small, single-purpose helpers for text, visibility, and accessibility. The escape hatch for edge cases that don't warrant a data-attribute.
+
+## Scope
+
+### In scope
+- Text alignment helpers
+- Visually-hidden (screen reader only)
+- Visibility toggles
+- Print styles
+- `prefers-reduced-motion` resets
+- `prefers-contrast` adjustments
+
+### Out of scope
+- Layout utilities (→ layouts layer)
+- Spacing/sizing utilities (use tokens directly)
+- Color utilities (use tokens directly)
+
+## Constraints
+
+- This layer should be minimal — most needs should be met by semantic elements + data attributes
+- References only semantic aliases from `01-tokens.css`