refactor(ui-css): split module styles

[Astro-Han]

Summary

• Split apps/desktop/src/renderer/styles/module-pages.css into focused module-page child stylesheets under styles/module-pages/.
• Move shared/global selectors out of styles/module-pages/ to their real owners: field focus, SettingsSelect, chat header, model switcher, and shared .detailPane chrome.
• Keep module-pages.css as the same renderer import slot, now only an ordered module-page import manifest.
• Add a renderer module styles contract so new module rules land in the owned child stylesheet and cross-owner selectors do not grow inside styles/module-pages/ again, including mixed comma selector lists.

Why

Refs #476.

PR1 made renderer CSS parseable and PR2 settled the cascade / bare-field reset path. This PR takes the next CSS hygiene step: module-pages.css was still a 2141-line mixed-domain stylesheet. Splitting it by ownership makes future CSS changes easier to review without changing the visual design.

Scope

Changed:

• apps/desktop/src/renderer/styles/module-pages.css now imports only true module-page child styles in a fixed order.
• apps/desktop/src/renderer/styles/module-pages/plan-reminders.css owns plan reminder styles.
• apps/desktop/src/renderer/styles/module-pages/capability-audit.css owns CapabilityAuditStrip styles.
• apps/desktop/src/renderer/styles/module-pages/module-shell.css owns .maka-module-* shell styles.
• apps/desktop/src/renderer/styles/module-pages/skills.css owns skill module styles.
• apps/desktop/src/renderer/styles/field-focus.css owns the shared renderer field focus rule from PR2.
• apps/desktop/src/renderer/styles/settings-select.css owns the shared SettingsSelect / grouped select menu chrome.
• apps/desktop/src/renderer/styles/chat-header.css now owns the .maka-chat-header* and chat status cluster rules.
• apps/desktop/src/renderer/styles/model-switcher.css owns the .maka-model-switcher* trigger chrome.
• apps/desktop/src/renderer/styles/base.css owns shared .detailPane sizing/overflow chrome.
• apps/desktop/src/main/__tests__/renderer-module-styles-contract.test.ts pins module-pages.css as an ordered import manifest and rejects global/shared/chat/model/select selectors under styles/module-pages/**, including mixed comma selector lists.
• apps/desktop/src/main/__tests__/renderer-important-audit-contract.test.ts now points the existing allowlist checks at the moved owner files.

Not included:

• No visual redesign.
• No selector renaming.
• No React architecture work from refactor(ui): React architecture debt cleanup (post #430 converge) #477.

Verification

• RED: renderer-module-styles-contract.test.js failed before the split because module-pages.css had no child imports and still contained selector rules.
• RED: owner contract failed before the review fix on field-focus.css, chat-header-bridge.css, model-switcher.css, .settingsSelect*, and .detailPane under styles/module-pages/**.
• RED: mixed selector-list fixture .foreign-owner, .maka-plan-card { ... } passed under the whole-rule.selector check; after splitting with postcss.list.comma, the same fixture fails on .foreign-owner, while .maka-plan-a, .maka-plan-b { ... } passes.
• Main sync: merged origin/main after fix(ui): visual audit round — list bullets, artifact toolbar, disclosure affordance #488 and mapped its old module-pages.css.maka-skill-featured-art adjustment into styles/module-pages/skills.css.
• Temporary declaration-equivalence check before initial split: parsed the original main:apps/desktop/src/renderer/styles/module-pages.css and the expanded split CSS with PostCSS; both had 1174 declarations, with 0 missing and 0 added.
• Temporary declaration-equivalence check after owner fix: expanded full renderer CSS before/after the owner move; both had 7546 declarations, with 0 missing and 0 added.
• node ../../worktree-bootstrap.mjs (inside the worktree; links @maka/* to this checkout and runs npm run rebuild)
• Commit-level check for refactor(ui-css): move shared styles to true owners: npm run -w @maka/desktop build:main && node --test apps/desktop/dist/main/__tests__/renderer-module-styles-contract.test.js apps/desktop/dist/main/__tests__/renderer-important-audit-contract.test.js apps/desktop/dist/main/__tests__/renderer-css-parse-contract.test.js apps/desktop/dist/main/__tests__/renderer-tailwind-compile-contract.test.js
• Commit-level check for test(ui-css): guard module style ownership: npm run -w @maka/desktop build:main && node --test apps/desktop/dist/main/__tests__/renderer-module-styles-contract.test.js
• Commit-level check for test(ui-css): split module owner selector lists: npm run -w @maka/desktop build:main && node --test apps/desktop/dist/main/__tests__/renderer-module-styles-contract.test.js apps/desktop/dist/main/__tests__/renderer-css-parse-contract.test.js apps/desktop/dist/main/__tests__/renderer-tailwind-compile-contract.test.js apps/desktop/dist/main/__tests__/renderer-important-audit-contract.test.js
• Post-main-sync CSS contracts: npm --workspace @maka/ui run build && npm run -w @maka/desktop build:main && node --test apps/desktop/dist/main/__tests__/renderer-module-styles-contract.test.js apps/desktop/dist/main/__tests__/renderer-css-parse-contract.test.js apps/desktop/dist/main/__tests__/renderer-tailwind-compile-contract.test.js apps/desktop/dist/main/__tests__/renderer-important-audit-contract.test.js apps/desktop/dist/main/__tests__/renderer-style-layer-cascade-contract.test.js apps/desktop/dist/main/__tests__/capability-audit-ui-contract.test.js (19 tests pass)
• node --test apps/desktop/dist/main/__tests__/renderer-css-parse-contract.test.js apps/desktop/dist/main/__tests__/renderer-tailwind-compile-contract.test.js apps/desktop/dist/main/__tests__/renderer-important-audit-contract.test.js apps/desktop/dist/main/__tests__/renderer-style-layer-cascade-contract.test.js apps/desktop/dist/main/__tests__/renderer-module-styles-contract.test.js
• npm run -w @maka/desktop build:renderer (passes; existing Vite chunk-size warning remains)
• Visual screenshots from this worktree:
  • node scripts/capture-screenshots.mjs --scenario module-skills --variant light-1280-motion
  • node scripts/capture-screenshots.mjs --scenario plan-reminders --variant light-1280-motion
  • node scripts/capture-screenshots.mjs --scenario provider-workspace --variant light-1280-motion
• npm run -w @maka/desktop test (1721 tests pass)

User-facing impact

No visual change intended. This is a CSS ownership split plus review fix. The declaration-equivalence checks and targeted screenshots above cover the affected module, capability audit, shared select, chat header, and model-switcher surfaces.

Reviewer notes

Commits are split by rollback reason:

• refactor(ui-css): split module styles splits the old catch-all stylesheet into initial focused files.
• refactor(ui-css): move shared styles to true owners addresses review feedback by moving global/shared/chat/model/select rules out of styles/module-pages/**.
• test(ui-css): guard module style ownership addresses review feedback by adding an owner-scoped contract for module-page child styles.
• test(ui-css): split module owner selector lists addresses review feedback by validating each comma-separated selector independently.
• chore: merge main into module styles split absorbs fix(ui): visual audit round — list bullets, artifact toolbar, disclosure affordance #488 and keeps its old module-pages.css visual fix under the new styles/module-pages/skills.css owner.