fix(fb-35): address PR #126 round 2 review

- wire schema: relax effective_end.minimum 1 → 0 + expand
  description to cover line-clamp + out-of-range sentinel
  (panic-fix R1 emits Some(0) when line_start=1 and range is
  beyond doc end — schema must accept it)
- tests: tighten first-chunk-target boundary test to assert ≤ 2
  total neighbors (3-chunk doc, N=2). Strict "first chunk →
  context_before empty" not assertable until chunks.ordinal
  column lands (R1 #9 architectural caveat)
- store: trim contradiction in list_chunk_ids_for_doc warning
  comment — drop "good enough for sequentially chunked
  markdown" phrase that conflicts with "hash sort dominates"
  paragraph above

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

crates/kebab-app/tests/fetch_integration.rs

@@ -310,10 +310,20 @@ fn fetch_chunk_context_at_first_chunk_clamps_lower_bound() {
             },
         )
         .unwrap();
-    // context_before may be empty if target is the first chunk;
-    // context_after should have ≤ 2 entries. Both clamped at doc boundaries.
+    // p9-fb-35 R2: doc has 3 chunks; ±2 should clamp the total
+    // neighbor count to ≤ 2 + 1 (= excludes target).
+    //
+    // ⚠ Strict "first-chunk → context_before is empty" cannot be
+    // asserted here yet because chunks.ordinal column does not exist
+    // — `list_chunk_ids_for_doc` orders by `(created_at, chunk_id)`
+    // and chunk_id is a blake3 hash, so the "First chunk" content
+    // may land at any hash-order position within the doc. The clamp
+    // logic itself is correct (target_idx ± n → [0..len]); we just
+    // can't pin which chunk is hash-order-first. Tracked as
+    // follow-up: V007 chunks.ordinal migration.
+    let total = result.context_before.len() + result.context_after.len();
     assert!(
-        result.context_before.len() + result.context_after.len() <= 4,
-        "doc boundary should clamp ±N to fit chunk count"
+        total <= 2,
+        "doc with 3 chunks ±2 → at most 2 neighbors (excludes target), got {total}"
     );
 }

crates/kebab-store-sqlite/src/documents.rs

@@ -389,10 +389,11 @@ impl SqliteStore {
     ///
     /// Real fix is a `chunks.ordinal` column (V007 migration) or sort
     /// by `chunks.source_spans_json[0]` start offset. Tracked as
-    /// follow-up; current behavior is good enough for sequentially
-    /// chunked markdown where created_at uniqueness varies, but PDFs
-    /// (page-aligned chunks) and large docs may surprise the agent.
-    /// See `tasks/HOTFIXES.md` if/when this is escalated.
+    /// follow-up. Until then `--context` neighbors are best-effort —
+    /// they may or may not align with document position depending on
+    /// whether `chunk_id` hash order happens to match insertion order
+    /// for that particular doc. Large markdown / PDF (page-aligned
+    /// chunks) likely re-orders. See `tasks/HOTFIXES.md` if escalated.
     pub fn list_chunk_ids_for_doc(
         &self,
         doc_id: &kebab_core::DocumentId,

docs/wire-schema/v1/fetch_result.schema.json

@@ -18,7 +18,7 @@
     "text":           { "type": "string", "description": "kind=doc/span: markdown text (truncated if budget tripped)" },
     "line_start":     { "type": ["integer", "null"], "minimum": 1, "description": "kind=span: requested start line (1-based)" },
     "line_end":       { "type": ["integer", "null"], "minimum": 1, "description": "kind=span: requested end line (1-based, inclusive)" },
-    "effective_end":  { "type": ["integer", "null"], "minimum": 1, "description": "kind=span: actual emitted end line after budget truncation" },
+    "effective_end":  { "type": ["integer", "null"], "minimum": 0, "description": "kind=span: actual end line of emitted text (1-based, inclusive). Equals `line_end` on full slice; less than `line_end` when (a) requested range exceeded total lines (line clamp) or (b) `--max-tokens` budget trimmed the tail. Special case: `line_start - 1` (which is 0 when line_start=1) signals the entire requested range was beyond doc end — returned `text` is empty." },
     "truncated":      { "type": "boolean", "description": "kind=doc/span: budget forced text truncation. Always false for chunk." }
   }
 }