fix(p10-1a-2): PR review round 1 — doc inconsistencies + observable backfill error path

PR #140 회차 1 actionable 7건 반영:
- docs/SMOKE.md: parser_version "code-rust-ast-v1" → "code-rust-v1" (chunker_version 과 혼동); jq path .citation.code_lang → .citation.lang (wire 의 code_lang 은 SearchHit top-level)
- docs/ARCHITECTURE.md: Mermaid pcode→ptypes 잘못된 edge → pcode→core 로 정정 (kebab-parse-code Cargo.toml 실제 dep 와 일치); 디렉토리 트리에서 code-rust-ast-v1 chunker 표기 위치 kebab-parse-code → kebab-chunk 로 정정
- crates/kebab-app/src/app.rs: backfill_repo 의 .ok().flatten() 실패 silent swallow → tracing::warn 로 관측 가능, 비-abort 의도 보존
- crates/kebab-parse-code/src/rust.rs: impl_item arm 의 "function_item 만 unit 생성" 1A scope 한정 주석을 외부에서도 보이도록 arm 상단에 한 줄 추가 (내부 주석은 유지)

verify: kebab-parse-code 7/7 / kebab-app --lib 51/51 / code_ingest_smoke 3/3 green; touched-crate clippy clean (재부팅 전 검증).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/ARCHITECTURE.md

@@ -98,7 +98,7 @@ flowchart TB
     ppdf --> ptypes
     pimg --> ptypes
     paud --> ptypes
-    pcode --> ptypes
+    pcode --> core
     norm --> ptypes
     embedlocal --> embed
     llmlocal --> llm
@@ -172,7 +172,7 @@ kebab/
 │   ├── kebab-eval/                                    # golden query runner + metrics (P5-1, P5-2)
 │   ├── kebab-parse-image/                             # ImageExtractor + Ollama OCR + caption (P6)
 │   ├── kebab-parse-pdf/                               # lopdf per-page text extractor (P7-1)
-│   ├── kebab-parse-code/                              # tree-sitter Rust AST extractor + code-rust-ast-v1 chunker (P10-1A-2)
+│   ├── kebab-parse-code/                              # tree-sitter Rust AST extractor (P10-1A-2); chunker lives in kebab-chunk
 │   ├── kebab-app/                                     # facade (P0 시그니처 + P3-5/P6-4/P7-3 본체)
 │   ├── kebab-tui/                                     # Ratatui shell + Library 패널 (P9-1)
 │   ├── kebab-mcp/                                     # stdio MCP server — tools: schema, doctor, search, ask (P9-FB-30)