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-chunk/src/md_heading_v1.rs

@@ -387,9 +387,7 @@ fn render_block_text(b: &Block) -> String {
         // alt keeps lexical search hits on filenames working even when
         // P6-1's filename auto-fill is bypassed.
         Block::ImageRef(i) => {
-            let alt = if !i.alt.is_empty() {
-                i.alt.clone()
-            } else {
+            let alt = if i.alt.is_empty() {
                 // P6-1 falls back to filename so this branch is
                 // defensive — keep it lest a future test fixture or
                 // synthetic block path skip the auto-fill.
@@ -399,17 +397,17 @@ fn render_block_text(b: &Block) -> String {
                     .filter(|s| !s.is_empty())
                     .unwrap_or("[image]")
                     .to_string()
+            } else {
+                i.alt.clone()
             };
             let ocr = i
                 .ocr
                 .as_ref()
-                .map(|o| o.joined.as_str())
-                .unwrap_or("");
+                .map_or("", |o| o.joined.as_str());
             let cap = i
                 .caption
                 .as_ref()
-                .map(|c| c.text.as_str())
-                .unwrap_or("");
+                .map_or("", |c| c.text.as_str());
             [alt.as_str(), ocr, cap]
                 .iter()
                 .filter(|s| !s.is_empty())