feat(rag): AnswerCitation inherits indexed_at + stale from hit (fb-32)

pack_context widened to carry indexed_at + stale alongside marker
and Citation. LLM-citation construction site now plumbs real values
from upstream SearchHit instead of the Task 6 UNIX_EPOCH placeholder.

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

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

@@ -116,6 +116,29 @@ pub fn mk_hit(
     workspace_path: &str,
     fusion_score: f32,
     heading: &[&str],
+) -> SearchHit {
+    mk_hit_with_indexed_at(
+        rank,
+        chunk_id,
+        doc_id,
+        workspace_path,
+        fusion_score,
+        heading,
+        time::OffsetDateTime::UNIX_EPOCH,
+    )
+}
+
+/// Build a `SearchHit` with an explicit `indexed_at` timestamp. Used by
+/// p9-fb-32 staleness tests so the pipeline sees realistic per-hit
+/// indexed_at values flowing through to `AnswerCitation`.
+pub fn mk_hit_with_indexed_at(
+    rank: u32,
+    chunk_id: &str,
+    doc_id: &str,
+    workspace_path: &str,
+    fusion_score: f32,
+    heading: &[&str],
+    indexed_at: time::OffsetDateTime,
 ) -> SearchHit {
     let p = WorkspacePath::new(workspace_path.to_string()).expect("workspace path valid");
     SearchHit {
@@ -143,8 +166,9 @@ pub fn mk_hit(
         index_version: IndexVersion("test-iv".to_string()),
         embedding_model: None,
         chunker_version: ChunkerVersion("v1".to_string()),
-        // p9-fb-32: synthetic test mock — staleness not exercised here.
-        indexed_at: time::OffsetDateTime::UNIX_EPOCH,
+        // p9-fb-32: pipeline post-processes `stale` from `indexed_at`
+        // + cfg threshold; tests configure both via this helper.
+        indexed_at,
         stale: false,
     }
 }

crates/kebab-rag/tests/pipeline.rs

@@ -9,7 +9,7 @@ mod common;
 use std::sync::Arc;
 use std::sync::atomic::Ordering;
 
-use common::{MockRetriever, RagEnv, id32, mk_hit};
+use common::{MockRetriever, RagEnv, id32, mk_hit, mk_hit_with_indexed_at};
 use kebab_core::{
     FinishReason, LanguageModel, Retriever, SearchMode, TokenChunk, TokenUsage,
 };
@@ -421,6 +421,73 @@ fn unfetchable_chunks_fall_back_to_no_chunks() {
     assert_eq!(env.count_answers(), 1, "answers row written for refusal");
 }
 
+// ── 16. p9-fb-32: AnswerCitation carries indexed_at + stale ──────────────
+//
+// Previously the LLM-citation construction site stamped `UNIX_EPOCH` +
+// `false` as a Task-7 placeholder. Task 7 plumbs real values from the
+// upstream `SearchHit` through `pack_context` so the wire-side
+// `AnswerCitation` reflects the document's actual age.
+
+#[test]
+fn grounded_citations_inherit_indexed_at_and_stale_from_hit() {
+    let env = RagEnv::new();
+    let cid = id32("c1");
+    let did = id32("d1");
+    env.seed_chunk(&cid, &did, "notes/a.md", "Apples are fruit.", &["Intro"]);
+    // 60 days old vs. the default 30-day threshold → stale.
+    let now = time::OffsetDateTime::now_utc();
+    let sixty_days_ago = now - time::Duration::days(60);
+    let hits = vec![mk_hit_with_indexed_at(
+        1, &cid, &did, "notes/a.md", 0.85, &["Intro"], sixty_days_ago,
+    )];
+    let retriever: Arc<dyn Retriever> = Arc::new(MockRetriever::new(hits));
+    let lm: Arc<dyn LanguageModel> = Arc::new(CountingLm::new("apples are fruit. [#1]"));
+    let pipeline = RagPipeline::new(env.config.clone(), retriever, lm, env.sqlite.clone());
+
+    let answer = pipeline.ask("apples", default_opts()).unwrap();
+    assert!(answer.grounded);
+    assert_eq!(answer.citations.len(), 1, "one cited marker [#1]");
+    let c = &answer.citations[0];
+    // indexed_at must be the value the retriever produced — NOT the
+    // UNIX_EPOCH placeholder the Task 6 cross-task patch left behind.
+    assert_eq!(
+        c.indexed_at, sixty_days_ago,
+        "AnswerCitation.indexed_at must inherit from SearchHit.indexed_at"
+    );
+    // 60d > default 30d threshold → stale.
+    assert!(
+        c.stale,
+        "60-day-old hit must surface stale=true on the AnswerCitation"
+    );
+}
+
+#[test]
+fn grounded_citations_not_stale_for_fresh_hit() {
+    let env = RagEnv::new();
+    let cid = id32("c1");
+    let did = id32("d1");
+    env.seed_chunk(&cid, &did, "notes/a.md", "Apples are fruit.", &["Intro"]);
+    // 1 day old vs. the default 30-day threshold → fresh.
+    let now = time::OffsetDateTime::now_utc();
+    let one_day_ago = now - time::Duration::days(1);
+    let hits = vec![mk_hit_with_indexed_at(
+        1, &cid, &did, "notes/a.md", 0.85, &["Intro"], one_day_ago,
+    )];
+    let retriever: Arc<dyn Retriever> = Arc::new(MockRetriever::new(hits));
+    let lm: Arc<dyn LanguageModel> = Arc::new(CountingLm::new("apples are fruit. [#1]"));
+    let pipeline = RagPipeline::new(env.config.clone(), retriever, lm, env.sqlite.clone());
+
+    let answer = pipeline.ask("apples", default_opts()).unwrap();
+    assert!(answer.grounded);
+    assert_eq!(answer.citations.len(), 1);
+    let c = &answer.citations[0];
+    assert_eq!(c.indexed_at, one_day_ago);
+    assert!(
+        !c.stale,
+        "1-day-old hit must NOT be stale at default 30d threshold"
+    );
+}
+
 // ── 15. snapshot Answer JSON stable ───────────────────────────────────────
 
 #[test]