refactor(rename): kb → kebab — binary, env vars, XDG paths, file renames

두 번째 commit. 사용자 facing surface (CLI binary, env vars, XDG paths)
+ 코드 안 single-letter token (`KB_`, `kb.sqlite`, `/kb/`, tracing
target) 일괄 rename. 그리고 3 개 file rename:

- 디자인 doc `2026-04-27-kb-final-form-design.md` →
  `2026-04-27-kebab-final-form-design.md`
- 최초 보고서 `kb_local_rust_report.md` → `kebab_local_rust_report.md`
- workspace ignore `.kbignore` → `.kebabignore`

## 변경

- `crates/kebab-cli/Cargo.toml`: `[[bin]] name = "kb"` → `"kebab"`.
- `crates/kebab-cli/src/main.rs`: `#[command(name = "kb", …)]` →
  `name = "kebab"`.
- 모든 `KB_*` env var (코드 + doc + 테스트) → `KEBAB_*`. apply_env
  prefix 매칭 + 30+ 개 setting 키 모두.
- XDG paths: `~/.config/kb` / `~/.local/share/kb` / `~/.cache/kb` /
  `~/.local/state/kb` → `~/.config/kebab` 등. config defaults +
  expand_path tests + paths.rs 의 hardcode 모두.
- SQLite filename: `kb.sqlite` → `kebab.sqlite` (`SQLITE_FILE` const
  + 테스트 hardcode 모두).
- tracing target: `target: "kb-*"` → `"kebab-*"` (10+ 곳).
- snapshot fixture: `.kbignore` → `.kebabignore` (`fixtures/source-fs/
  tree-1.snapshot.json` 갱신).

## 검증

- `cargo test --workspace -j 1` clean (linker OOM 회피 위해 직렬).
- `cargo clippy --workspace --all-targets -- -D warnings` clean.

다음 commit 에서 docs sweep.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

crates/kebab-eval/src/runner.rs

@@ -13,7 +13,7 @@ use kebab_store_sqlite::{EvalRunRow, SqliteStore};
 use time::OffsetDateTime;
 
 use crate::loader::{load_golden_set, validate_against_db};
-use crate::metrics::{DEFAULT_GOLDEN_PATH, KB_EVAL_GOLDEN};
+use crate::metrics::{DEFAULT_GOLDEN_PATH, KEBAB_EVAL_GOLDEN};
 use crate::types::{EvalRun, EvalRunOpts, GoldenQuery, QueryResult};
 
 /// Convert a wall-clock duration since `start` into milliseconds clamped
@@ -46,7 +46,7 @@ pub fn run_eval_with_config(cfg: &kebab_config::Config, opts: &EvalRunOpts) -> R
     let golden_path = resolve_golden_path();
     let queries = load_golden_set(&golden_path).with_context(|| {
         format!(
-            "load golden set from {} (override via KB_EVAL_GOLDEN)",
+            "load golden set from {} (override via KEBAB_EVAL_GOLDEN)",
             golden_path.display()
         )
     })?;
@@ -55,7 +55,7 @@ pub fn run_eval_with_config(cfg: &kebab_config::Config, opts: &EvalRunOpts) -> R
     // ── 2. Mint identifiers + open store ──────────────────────────────────
     let run_id = mint_run_id();
     let created_at = OffsetDateTime::now_utc();
-    let commit_hash = std::env::var("KB_COMMIT_HASH")
+    let commit_hash = std::env::var("KEBAB_COMMIT_HASH")
         .ok()
         .filter(|s| !s.is_empty());
 
@@ -110,7 +110,7 @@ pub fn run_eval_with_config(cfg: &kebab_config::Config, opts: &EvalRunOpts) -> R
 
     let duration_ms = elapsed_ms_u32(started);
     tracing::info!(
-        target: "kb-eval",
+        target: "kebab-eval",
         run_id = %run_id,
         suite = %opts.suite,
         queries = per_query.len(),
@@ -136,11 +136,11 @@ fn mint_run_id() -> String {
     format!("run_{id}")
 }
 
-/// Resolve the golden YAML path. Honors the `KB_EVAL_GOLDEN` env
+/// Resolve the golden YAML path. Honors the `KEBAB_EVAL_GOLDEN` env
 /// override; otherwise relative to CWD. The path is NOT expanded for
 /// `~` / `${...}` placeholders — direct file paths only.
 fn resolve_golden_path() -> PathBuf {
-    match std::env::var(KB_EVAL_GOLDEN) {
+    match std::env::var(KEBAB_EVAL_GOLDEN) {
         Ok(s) if !s.is_empty() => PathBuf::from(s),
         _ => PathBuf::from(DEFAULT_GOLDEN_PATH),
     }