feat(chunk): integrate lindera korean morphological tokenizer

V009 의 tokenized_korean_text column 에 들어갈 morpheme sequence
를 lindera ko-dic 으로 분해. chunk builder pipeline 의 chunk 생성
직후 시점에서 호출 → chunk struct 의 field 에 pre-fill → store
의 put_chunks 가 단일 transaction 안에서 INSERT.

- crates/kebab-core/src/chunk.rs: Chunk struct 에
  tokenized_korean_text: Option<String> field 추가 (#[serde(default)]).
- crates/kebab-chunk/src/lib.rs: tokenize_korean_morphological()
  helper + OnceLock 캐싱 + fallback (None) 정책.
- crates/kebab-chunk/Cargo.toml: lindera features = ["embed-ko-dic"]
  추가 (DictionaryKind::KoDic 활성화에 필요).
- 모든 chunker (tier2_shared, md_heading_v1, pdf_page_v1, 9개
  code AST v1): Chunk 리터럴에 tokenized_korean_text pre-fill.
- crates/kebab-store-sqlite/src/documents.rs::put_chunks: INSERT
  SQL column list + placeholder + binding 갱신 (12번째 column).
- crates/kebab-chunk/tests/tokenize_korean.rs: 단위 테스트 2개.

lindera 3.0.7 API 정정: load_dictionary_from_kind →
load_embedded_dictionary, Token.text → Token.surface.

Spec: docs/superpowers/specs/2026-05-28-v0.20.x-korean-morphological-tokenizer-spec.md §6.2
Plan: docs/superpowers/plans/2026-05-28-v0.20.x-korean-morphological-tokenizer-plan.md (S3)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/kebab-chunk/src/code_rust_ast_v1.rs

@@ -147,6 +147,7 @@ fn make_chunk(
         chunk_id,
         doc_id: DocumentId(doc.doc_id.0.clone()),
         block_ids: block_ids.to_vec(),
+        tokenized_korean_text: None,
         text,
         heading_path: Vec::new(),
         source_spans: vec![span],