chore: workspace-wide cleanup — clippy::pedantic baseline + auto-fix

cut PR v0.18.0 전 마지막 정리. 사용자 요청: "전체 코드베이스를 깔끔하고 알아보기 쉽게".

## Workspace lints

- `Cargo.toml` 의 `[workspace.lints.clippy]` 에 `pedantic = "warn"` (priority -1) + 의도적 allow-list 추가:
  - cast_possible_truncation / cast_possible_wrap / cast_sign_loss / cast_precision_loss — ONNX i64 / hash modular reduction 등 의도적 truncation.
  - doc_markdown / missing_errors_doc / missing_panics_doc — cosmetic doc style.
  - too_many_lines / module_name_repetitions / must_use_candidate / needless_pass_by_value / manual_let_else / items_after_statements / similar_names — informational only.
  - format_collect / match_wildcard_for_single_variants / trivially_copy_pass_by_ref / unnecessary_wraps — intentional patterns (exhaustive match, future Result variants 등).
  - default_trait_access — `Foo::default()` 가 idiomatic.
  - float_cmp — NLI / RRF score 의 explicit threshold 비교 의도.
  - struct_excessive_bools / case_sensitive_file_extension_comparisons / naive_bytecount / ignore_without_reason — domain-specific 의도.
  - format_push_string / return_self_not_must_use / match_same_arms — builder / wire-label / hot-path 패턴 보존.
  - needless_continue / used_underscore_binding / nonminimal_bool / unreadable_literal / many_single_char_names / doc_link_with_quotes / assigning_clones / collapsible_str_replace / trivial_regex / elidable_lifetime_names / range_plus_one / explicit_iter_loop / implicit_hasher / ref_option — remaining low-value style.
- 각 24 crate `Cargo.toml` 에 `[lints] workspace = true` 추가.

## Auto-fix

`cargo clippy --workspace --all-targets --fix` 적용 — 128 files changed, 552 insertions / 472 deletions. 주로:
- uninlined_format_args (~18): `format!("{}", x)` → `format!("{x}")`.
- redundant_closure_for_method_calls (~33): `.map(|x| x.foo())` → `.map(T::foo)`.
- 그 외 mechanical refactor.

## 검증

- `cargo clippy --workspace --all-targets -j 1 -- -D warnings` clean (pedantic + 모든 lint group).
- `cargo test --workspace --no-fail-fast -j 1` — **1293 tests pass + 1 pre-existing flaky fail** (`kebab-mcp::tools_call_ask_multi_hop::ask_tool_routes_multi_hop_true_to_decompose_first`, HOTFIX candidate, cleanup 무관). 회귀 0.

Wire 영향: 없음.
Behavior 영향: 없음 (mechanical refactor only).

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

crates/kebab-search/Cargo.toml

@@ -36,3 +36,6 @@ tempfile        = { workspace = true }
 # The mock-retriever unit tests (the bulk of the hybrid suite) do not
 # need either, but the integration / snapshot lane does.
 kebab-embed = { path = "../kebab-embed", features = ["mock"] }
+
+[lints]
+workspace = true

crates/kebab-search/src/hybrid.rs

@@ -601,7 +601,7 @@ mod tests {
         let h = HybridRetriever::with_policy(lex, vec, rrf_policy(60), 5);
         let out = h.search(&make_query(SearchMode::Hybrid, 5)).unwrap();
         let a = out.iter().find(|h| h.chunk_id.0 == "aaaa").unwrap();
-        let actual = a.retrieval.fusion_score as f64;
+        let actual = f64::from(a.retrieval.fusion_score);
         // Tolerance: the score is computed in f64 and cast to f32 at
         // the API boundary, so any discrepancy must fit within f32
         // precision. `1e-7` is below `f32::EPSILON` (~1.19e-7), which
@@ -694,7 +694,7 @@ mod tests {
         let h = HybridRetriever::with_policy(lex, vec, rrf_policy(60), 4);
         let out = h.search(&make_query(SearchMode::Hybrid, 4)).unwrap();
         let mut ids: Vec<&str> = out.iter().map(|h| h.chunk_id.0.as_str()).collect();
-        ids.sort();
+        ids.sort_unstable();
         assert_eq!(ids, vec!["aaaa", "bbbb", "cccc", "dddd"]);
     }
 

crates/kebab-search/src/lexical.rs

@@ -457,7 +457,7 @@ fn run_query(
         .prepare(&sql)
         .context("kb-search lexical: prepare FTS5 statement")?;
     let rows = stmt
-        .query_map(params_from_iter(params.iter().map(|b| b.as_ref())), row_from_sql)
+        .query_map(params_from_iter(params.iter().map(std::convert::AsRef::as_ref)), row_from_sql)
         .context("kb-search lexical: execute FTS5 query")?;
     let mut out: Vec<RawRow> = Vec::new();
     for r in rows {

crates/kebab-search/tests/common/mod.rs

@@ -37,12 +37,10 @@ use tempfile::TempDir;
 pub fn require_avx_or_panic() {
     #[cfg(target_arch = "x86_64")]
     {
-        if !std::is_x86_feature_detected!("avx") {
-            panic!(
-                "kb-search hybrid integration test requires AVX-capable hardware; \
-                 host CPU lacks AVX. Run on an AVX-capable machine."
-            );
-        }
+        assert!(std::is_x86_feature_detected!("avx"), 
+            "kb-search hybrid integration test requires AVX-capable hardware; \
+             host CPU lacks AVX. Run on an AVX-capable machine."
+        );
     }
 }
 
@@ -285,7 +283,7 @@ impl HybridEnv {
             vector,
             doc_id: DocumentId(doc_id.to_string()),
             text: text.to_string(),
-            heading_path: heading_path.iter().map(|s| s.to_string()).collect(),
+            heading_path: heading_path.iter().map(std::string::ToString::to_string).collect(),
             model_id: EmbeddingModelId(TEST_MODEL_ID.to_string()),
             model_version: EmbeddingVersion("v1".to_string()),
             dimensions: TEST_DIMENSIONS,

crates/kebab-search/tests/hybrid.rs

@@ -186,14 +186,12 @@ fn hybrid_snapshot_run_1() {
     // Refuse to silently "pass" against the committed placeholder. The
     // placeholder JSON carries a `_comment` field with regeneration
     // instructions; production fixtures (a captured list) do not.
-    if expected.get("_comment").is_some() {
-        panic!(
-            "snapshot fixture is a placeholder — regenerate on AVX hardware then commit. \
-             Path: {}. To regenerate: \
-             `KEBAB_UPDATE_SNAPSHOTS=1 cargo test -p kb-search -- --ignored hybrid_snapshot`.",
-            fixture.display()
-        );
-    }
+    assert!(!expected.get("_comment").is_some(), 
+        "snapshot fixture is a placeholder — regenerate on AVX hardware then commit. \
+         Path: {}. To regenerate: \
+         `KEBAB_UPDATE_SNAPSHOTS=1 cargo test -p kb-search -- --ignored hybrid_snapshot`.",
+        fixture.display()
+    );
 
     assert_eq!(
         actual, expected,