fix(sw): refine process header empty title states and UI guidance

- AI_GUIDE stage 5 "Header 전용 스타일의 적용 범위": header-only styles stay
  in the header (SW SWHeader / SWProcessHeader / SWViewerHeader, Web GNB /
  LNBMobileHeader / DashboardHeader); no header CSS or tokens on body UI,
  no global overrides, layout-only joins, package-shared tokens unchanged,
  whole-screen use only on explicit request. Synced to the 4 package
  copies; referenced from stage 6, SW and Web AI_USAGE §3
- SWProcessHeader: with documentTitle "" the file name keeps #AEDBCC on
  hover and a default cursor (root data-document-untitled). The button,
  focus and onDocumentClick are kept; a real file name keeps the yellow
  hover and pointer. Visual vs. click difference recorded as a UX item
- Step enablement documented as implemented: only an explicit disabled
  (step, group, process, header) turns steps off; project / file state
  never does; selection is activeStepId + onStepSelect (also for host
  previous / next); no activeStepId and empty groups described
- Regression check tests/process-header-states.check.mjs (15/15);
  typecheck:sw, build:sw, check:ai-docs pass; public-api keeps its 3
  existing failures, none new

packages/ui/ai/AI_USAGE.md

@@ -54,6 +54,7 @@ import { applyRuntimeTheme, resetRuntimeTheme, loadRuntimeTheme } from "@hm-desi
 - Light/Dark 분기 없음. `dark:` 분기·Dark Token을 추가하지 않는다.
 - 테마 변경은 Runtime Theme(`applyRuntimeTheme(root, theme)`, `loadRuntimeTheme(root, url)`)만 쓴다. `theme`은 `{ schemaVersion: 1, tokens: { "color.bg.content": "#…" } }` 형식이며 키는 `runtimeThemeContract`에 있는 것만 유효하다.
 - 한 페이지의 Navigation은 GNB / LNB / DASHBOARD 중 하나다([COMPOSITION_PATTERNS.md](./COMPOSITION_PATTERNS.md) §1).
+- `GNB`·`LNBMobileHeader`·`DashboardHeader`의 전용 스타일은 Header 영역에만 쓴다. 본문 UI에 Header 모양을 적용하지 않는다([AI_GUIDE.md](./AI_GUIDE.md) 5단계 "Header 전용 스타일의 적용 범위").
 
 ## 4. 접근성 기본