refactor(desktop): remove dead shell CSS recipes and close check-dead-css blind spots

[Astro-Han]

Summary

maka-tokens.css carries ~13 dead legacy shell "recipes" plus 2 dead tokens, and scripts/check-dead-css.mjs cannot see them due to three blind spots in the scanner.

Evidence

Dead rules with zero className consumers anywhere in apps/desktop/src + packages/ui/src (verified per-class, exact match, not substring):

• .maka-shell (maka-tokens.css:1208), .maka-shell-rail-right (1217), .maka-sidebar + header/section/row/button state family (1223-1281), .maka-titlebar (1294,1304), .maka-chat (1310), .maka-composer-toolbar (1408), .maka-shimmer (1469)
• Tokens --w-rail/--w-sidebar (649-650) are read only by those dead rules.
• Live for contrast: .maka-main (mcp-page.tsx:306), .maka-code (artifact-preview.tsx:77), .maka-turn (packages/ui/chat-turn.tsx:398).

Scanner blind spots (scripts/check-dead-css.mjs):

1. Class selectors are collected only from styles/ + reference-shell.css; maka-tokens.css is scanned for tokens only.
2. Consumer check is substring sourceBlob.includes(cls) — maka-shell is "used" by maka-shell-astryx, maka-sidebar by maka-sidebar-update-button, maka-titlebar by maka-titlebar-action, maka-chat by maka-chat-message-*. .maka-composer-toolbar and .maka-shimmer have no substring consumer at all — they are invisible purely due to blind spot 1.
3. Tokens are seeded as "live" by reads inside the token sheet itself.

--check currently prints "no dead classes or tokens found ✓" while ~13 dead rules coexist — the baseline gate is blind for this sheet.

Fix

• Delete the dead rules and --w-rail/--w-sidebar; fold @keyframes maka-shimmer into functional-motion.stories.tsx (its only consumer) or delete it, and fix the stale governance comment.
• Fix the scanner: include maka-tokens.css class selectors in the scan, switch the consumer check to word-boundary matching (\bmaka-shell\b).
• While in the sheet: apps/desktop/src/renderer/astryx-theme/maka.d.ts:7 references ./maka.variants.d.ts, which @astryxdesign/cli 0.2.0 no longer emits (scripts/build-astryx-theme.mjs:30-33); strip the reference during theme build post-processing (currently masked by skipLibCheck).

Owner

apps/desktop renderer (CSS) + scripts/check-dead-css.mjs.

Acceptance

• npm run check:release / check-dead-css --check flags dead classes in maka-tokens.css (fixture covering prefix-collision and token-read-only-by-dead-rules).
• Removing the dead rules causes no visual change (no live consumer).