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/layouts/spec.md

@@ -0,0 +1,42 @@
+# Spec: Layouts (Layer 11)
+
+File: `src/layers/11-layout.css`
+
+## Purpose
+
+Page-level layout systems. Controls how landmarks arrange on the page. Selected via `data-layout` attribute.
+
+## Layout Types
+
+### `data-layout="docs"` — Documentation
+Three-column layout: sidebar navigation, main content, table of contents. The standard documentation pattern.
+
+### `data-layout="console"` — Console
+Docs variant: sidebar flush to viewport edge. Prototype — not yet used in production.
+
+### `data-layout="grid-2"` / `data-layout="grid-3"` — Grids
+Multi-column content grids for cards, galleries, dashboards.
+
+### Essay layout
+Long-form prose with table of contents. Wider reading measure, typographic refinements.
+
+### Prose width
+`--width-prose` constrains content to readable line length within any layout.
+
+## Scope
+
+### In scope
+- `data-layout` attribute styling
+- Prose width constraints
+- Responsive layout breakpoints
+- Essay/long-form layout variant
+
+### Out of scope
+- Landmark styling within layouts (→ landmarks layer)
+- Navigation behavior within layouts (→ navigation layer)
+
+## Constraints
+
+- References only semantic aliases from `01-tokens.css`
+- Layouts must degrade gracefully on mobile (single column)
+- No layout should require JavaScript