[08-Documenter] #311 설계서 Approved + reference + 사용자 가이드 FAQ

- docs/design/311-llm-warmup/ 3파일 상태 Draft → Approved (v0.4.1)
- docs/reference/311-llm-warmup.md 신규 (상태 머신, API, UI binding,
  마이크로카피, 테스트)
- docs/guides/ai-chat-using.md 헤더 + FAQ 2건 추가 (warmup 인지/회복)

Refs #311

docs/design/311-llm-warmup/README.md

@@ -1,8 +1,8 @@
 # 설계서: ChatScreen LLM warm-up (#311)
 
-> **상태**: Draft
-> **작성**: [AI] Architect · **최종수정**: 2026-06-15
-> **추적성** — Redmine: #311 · 관련 ADR: 없음 (Backward-compatible 추가)
+> **상태**: Approved (v0.4.1, 2026-06-15)
+> **작성**: [AI] Architect · **최종수정**: 2026-06-15 (08-Documenter 마감)
+> **추적성** — Redmine: #311 · 관련 ADR: 없음 (Backward-compatible 추가) · Release: v0.4.1 (`121108f`)
 > · 구현 파일: `app/lib/state/chat_warmup_provider.dart` (신규) · `app/lib/data/ai/llm_service.dart` (수정) · `app/lib/data/ai/model_lifecycle.dart` (`quickCheck` 추가) · `app/lib/data/ai/gemma_llm_service.dart` (concurrent load guard) · `app/lib/ui/screens/chat_screen.dart` (warmup binding)
 > · 테스트: `app/test/state/chat_warmup_test.dart` (신규) · `app/test/data/ai/model_lifecycle_test.dart` (quickCheck 케이스 추가) · `app/test/ui/chat_screen_test.dart` (warmup 라벨/disabled 케이스 추가)
 

docs/design/311-llm-warmup/fn-chat_warmup_controller.md

@@ -1,6 +1,6 @@
 # 함수 설계서: `ChatWarmupController.start` (#311)
 
-> **부모 설계서**: ./README.md · **상태**: Draft
+> **부모 설계서**: ./README.md · **상태**: Approved (v0.4.1, 2026-06-15)
 > **작성**: [AI] Architect · **구현**: `app/lib/state/chat_warmup_provider.dart:start` · **테스트**: `app/test/state/chat_warmup_test.dart`
 
 ## 1. 시그니처

docs/design/311-llm-warmup/fn-concurrent_load_guard.md

@@ -1,6 +1,6 @@
 # 함수 설계서: `GemmaLlmService.load` concurrent guard (#311)
 
-> **부모 설계서**: ./README.md · **상태**: Draft
+> **부모 설계서**: ./README.md · **상태**: Approved (v0.4.1, 2026-06-15)
 > **작성**: [AI] Architect · **구현**: `app/lib/data/ai/gemma_llm_service.dart:load` (수정) · **테스트**: `app/test/data/ai/gemma_llm_service_test.dart` (concurrent 케이스 추가) / `chat_warmup_test.dart` (시뮬)
 
 ## 1. 시그니처