feat(cli): kebab ask citation block (p9-fb-20)

답변 출력 후 `근거:` 절 — `[N] <full path>#<fragment>  (score=<s>)`
한 줄씩. spec p9-fb-20 의 핵심 (full path 가독성) 충족.

신규 flag:
- --show-citations: default ON. 답변 후 citation block 출력.
- --hide-citations: 답변 본문만 출력 (pipe 시 다른 도구가 trailing
  metadata 안 받기 원할 때).

`--json` 모드 무영향 — citations 가 wire payload 에 항상 포함되므로
flag 가 영향 X (외부 wrapper 호환성).

spec p9-fb-20 의 \"TUI citation pane + jump (Enter/o editor jump,
i inspect)\" 부분은 본 PR scope 에서 제외 — TUI 의 기존
render_citations_or_explain (P9-3) 가 이미 citation list 표시,
추가 fold/jump 는 후속 task. 사용자 도그푸딩 priority 5위 의
핵심 = \"full path 가독성\" 이라 CLI block 만으로 충분.

Plan 갱신:
- p9-fb-20 status planned → in_progress. 머지 후 한 줄 commit
  으로 completed flip.

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

crates/kebab-cli/src/main.rs

@@ -99,6 +99,21 @@ enum Cmd {
 
         #[arg(long)]
         seed: Option<u64>,
+
+        /// p9-fb-20: print the `근거:` block (full path / line range
+        /// / score, one per line) after the answer. Default on.
+        /// `--json` mode is unaffected — citations are always
+        /// included in the wire payload regardless of this flag.
+        #[arg(long, action = clap::ArgAction::SetTrue,
+              conflicts_with = "hide_citations",
+              default_value_t = true)]
+        show_citations: bool,
+
+        /// p9-fb-20: opt out of the `근거:` block (sticky-overrides
+        /// `--show-citations`). Useful when piping the answer body
+        /// to another tool that doesn't want trailing metadata.
+        #[arg(long)]
+        hide_citations: bool,
     },
 
     /// Wipe XDG data dirs (and optionally the Lance vector store) so the
@@ -418,6 +433,8 @@ fn run(cli: &Cli) -> anyhow::Result<()> {
             explain,
             temperature,
             seed,
+            show_citations,
+            hide_citations,
         } => {
             let cfg = kebab_config::Config::load(cli.config.as_deref())?;
             let opts = kebab_app::AskOpts {
@@ -442,6 +459,25 @@ fn run(cli: &Cli) -> anyhow::Result<()> {
                 println!("{}", serde_json::to_string(&wire::wire_answer(&ans))?);
             } else {
                 println!("{}", ans.answer);
+                // p9-fb-20: print the citation block after the
+                // answer body when --hide-citations is not set
+                // (--show-citations is the default). Skipped on
+                // refusal-with-zero-citations to avoid an empty
+                // `근거:` header.
+                let print_citations = *show_citations && !*hide_citations;
+                if print_citations && !ans.citations.is_empty() {
+                    println!();
+                    println!("근거:");
+                    for (idx, c) in ans.citations.iter().enumerate() {
+                        let marker = c.marker.as_deref().unwrap_or(&format!("{}", idx + 1)).to_string();
+                        println!(
+                            "  [{}] {}  (score={:.2})",
+                            marker,
+                            c.citation.to_uri(),
+                            ans.retrieval.top_score,
+                        );
+                    }
+                }
             }
             // Refusal → exit 1.
             if !ans.grounded {