refactor(search): alias lexical arm 제거

run_alias_query / merge_body_alias 제거, 검색을 body_rows 직접 사용으로
단순화. build_match_string_for_column 의 column 매개변수 인라인(text 고정).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/kebab-search/src/lexical.rs

@@ -123,29 +123,7 @@ impl Retriever for LexicalRetriever {
         };
 
         let conn = self.store.read_conn();
-        let body_rows = run_query(&conn, &match_str, self.snippet_words, filters, fetch_limit)?;
-        // doc-side expansion (V010): re-run the same query against the
-        // `aliases` column of `chunk_aliases_fts`. Empty table → 0 rows →
-        // `body_rows` unchanged (regression-safe). body wins; alias-only
-        // chunks are appended so a term present only in a chunk's aliases
-        // still enters the pool.
-        //
-        // Raw mode (`'...'`) is a body-FTS5 escape hatch and may reference
-        // body-only columns (e.g. `heading_path : ...`) that don't exist on
-        // `chunk_aliases_fts`. Running such an expression against the alias
-        // table is a hard FTS5 error, so we skip the alias channel for raw
-        // queries — they target the body intentionally.
-        let alias_rows = if strip_single_quotes(query.text.trim()).is_some() {
-            Vec::new()
-        } else {
-            match build_match_string_for_column(&query.text, "aliases") {
-                Some(alias_match) => {
-                    run_alias_query(&conn, &alias_match, self.snippet_chars, fetch_limit)?
-                }
-                None => Vec::new(),
-            }
-        };
-        let raw_rows = merge_body_alias(body_rows, alias_rows, fetch_limit);
+        let raw_rows = run_query(&conn, &match_str, self.snippet_words, filters, fetch_limit)?;
 
         let mut hits: Vec<SearchHit> = Vec::with_capacity(raw_rows.len().min(k));
         let mut rank: u32 = 0;
@@ -228,16 +206,6 @@ impl Retriever for LexicalRetriever {
 ///   match is scoped to the body column. FTS5's column-filter syntax
 ///   accepts an arbitrary OR/AND sub-expression inside the parens.
 fn build_match_string(text: &str) -> Option<String> {
-    build_match_string_for_column(text, "text")
-}
-
-/// Column-parameterized variant of [`build_match_string`]. `column` is the
-/// FTS5 column-filter prefix the combined expression is scoped to — `"text"`
-/// for the body channel (`chunks_fts`) or `"aliases"` for the doc-side
-/// expansion channel (`chunk_aliases_fts`, V010). Raw mode (`'...'`) is still
-/// passed through verbatim without any column scoping, so an explicit
-/// user-supplied column filter is honored unchanged.
-fn build_match_string_for_column(text: &str, column: &str) -> Option<String> {
     let trimmed = text.trim();
     if trimmed.is_empty() {
         return None;
@@ -274,7 +242,7 @@ fn build_match_string_for_column(text: &str, column: &str) -> Option<String> {
         (Some(w), Some(a)) if w == a => w,
         (Some(w), Some(a)) => format!("({w}) OR ({a})"),
     };
-    Some(format!("{column} : ({expression})"))
+    Some(format!("text : ({expression})"))
 }
 
 /// Return `Some(inner)` if `s` is wrapped in a matching pair of single
@@ -512,77 +480,6 @@ fn row_from_sql(row: &Row<'_>) -> rusqlite::Result<RawRow> {
     })
 }
 
-/// Search the doc-side expansion channel (`chunk_aliases_fts`, V010) and
-/// build [`RawRow`]s with the **same 10-column shape** as [`run_query`] so
-/// `row_from_sql` / `build_hit` can be reused verbatim. The snippet is taken
-/// from the body (`substr(c.text, 1, ?)`) rather than the alias text so the
-/// rendered hit stays consistent with the body channel. When
-/// `chunk_aliases_fts` is empty (no chunk carries aliases) this returns 0
-/// rows, making the merge a no-op (regression-safe).
-///
-/// 1차는 filters 미적용 — body 채널이 필터를 적용하고, 별칭 경로는 pool 진입
-/// (회수)이 목적이다(측정 후 필요 시 filters 공유). `bm25(chunk_aliases_fts)`
-/// 오름차순 + `af.chunk_id` tie-break 로 결정적 순서.
-fn run_alias_query(
-    conn: &Connection,
-    match_str: &str,
-    snippet_chars: usize,
-    fetch_limit: usize,
-) -> Result<Vec<RawRow>> {
-    let sql = "SELECT \
-            af.chunk_id, af.doc_id, \
-            bm25(chunk_aliases_fts) AS score, \
-            substr(c.text, 1, ?) AS snippet, \
-            c.heading_path_json, c.section_label, c.source_spans_json, \
-            c.chunker_version, \
-            d.workspace_path, d.updated_at \
-         FROM chunk_aliases_fts af \
-         JOIN chunks c    ON c.chunk_id = af.chunk_id \
-         JOIN documents d ON d.doc_id = af.doc_id \
-         WHERE chunk_aliases_fts MATCH ? \
-         ORDER BY score, af.chunk_id LIMIT ?";
-    let params: Vec<Box<dyn ToSql>> = vec![
-        Box::new(snippet_chars as i64),
-        Box::new(match_str.to_owned()),
-        Box::new(i64::try_from(fetch_limit).unwrap_or(i64::MAX)),
-    ];
-    let mut stmt = conn
-        .prepare(sql)
-        .context("kb-search lexical: prepare alias FTS5 statement")?;
-    let rows = stmt
-        .query_map(
-            params_from_iter(params.iter().map(std::convert::AsRef::as_ref)),
-            row_from_sql,
-        )
-        .context("kb-search lexical: execute alias FTS5 query")?;
-    let mut out: Vec<RawRow> = Vec::new();
-    for r in rows {
-        out.push(r.context("kb-search lexical: read alias row")?);
-    }
-    Ok(out)
-}
-
-/// Merge body + alias rows: body rows first (already bm25-ordered), then
-/// any alias-only chunk (not already present in the body result) appended in
-/// alias-relevance order. Capped at `limit`. An empty `alias` slice leaves
-/// `body` unchanged, so an empty `chunk_aliases_fts` reproduces the
-/// pre-expansion behavior exactly.
-fn merge_body_alias(body: Vec<RawRow>, alias: Vec<RawRow>, limit: usize) -> Vec<RawRow> {
-    use std::collections::HashSet;
-    let mut seen: HashSet<String> = body.iter().map(|r| r.chunk_id.clone()).collect();
-    let mut out = body;
-    for r in alias {
-        if out.len() >= limit {
-            break;
-        }
-        if seen.insert(r.chunk_id.clone()) {
-            out.push(r);
-        }
-    }
-    out.truncate(limit);
-    out
-}
-
 // ── Hit construction ─────────────────────────────────────────────────────
 
 fn build_hit(