review(p9-4): 회차 1 지적 반영

blocks / embeddings 섹션의 count 라인이 collapse 검사 *밖* 에서 push
되어 collapsed 상태에서 부분만 사라지던 일관성 깨짐. fix: count 를
section header 에 inline 으로 (`▾ blocks (N)`, `▾ embeddings (N)`),
body 만 collapse 검사 안. 새 helper `push_section_header_with_count`
가 둘 다 통일.

회귀 테스트 보강:
- doc_view_collapse_hides_section_body: collapsed 상태에서 \"blocks (2)\"
  inline count 표시 + \"Heading L1\" body 숨김 검증.
- chunk_view_renders_text_and_block_ids: \"embeddings (2)\" inline
  count 검증.

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

crates/kebab-tui/tests/inspect.rs

@@ -264,16 +264,25 @@ fn doc_view_collapse_hides_section_body() {
     }
     let pre = render_to_string(&app, 100, 30);
     assert!(pre.contains("kb-source-fs"), "before collapse");
+    assert!(pre.contains("Heading L1"), "blocks body before collapse");
     handle_key_inspect(
         &mut app,
         KeyEvent::new(KeyCode::Char('c'), KeyModifiers::NONE),
     );
     let post = render_to_string(&app, 100, 30);
     assert!(post.contains("metadata"), "section header still visible");
+    assert!(
+        post.contains("blocks (2)"),
+        "blocks count visible inline on collapsed header: {post}"
+    );
     assert!(
         !post.contains("kb-source-fs"),
         "provenance body hidden after collapse: {post}"
     );
+    assert!(
+        !post.contains("Heading L1"),
+        "blocks body hidden after collapse (count must collapse with body): {post}"
+    );
 }
 
 #[test]
@@ -290,8 +299,8 @@ fn chunk_view_renders_text_and_block_ids() {
     assert!(rendered.contains("Line 1-5"), "source span described");
     assert!(rendered.contains("chunk body line one"), "text body rendered");
     assert!(
-        rendered.contains("block_ids = 2"),
-        "block_id count rendered"
+        rendered.contains("embeddings (2)"),
+        "block_id count rendered inline on embeddings header"
     );
 }