Phase 28-36 body of work

Accumulated since a6f12e2 (Phase 21 Rust port + Phase 27 versioning):

- Phase 36: embed_semaphore on VectorState (permits=1) serializes
  seed embed calls — prevents sidecar socket collisions under
  concurrent /seed stress load
- Phase 31+: run_stress.ts 6-task diverse stress scaffolding;
  run_e2e_rated.ts + orchestrator.ts tightening
- Catalog dedupe cleanup: 16 duplicate manifests removed; canonical
  candidates.parquet (10.5MB -> 76KB) + placements.parquet (1.2MB ->
  11KB) regenerated post-dedupe; fresh manifests for active datasets
- vectord: harness EvalSet refinements (+181), agent portfolio
  rotation + ingest triggers (+158), autotune + rag adjustments
- catalogd/storaged/ingestd/mcp-server: misc tightening
- docs: Phase 28-36 PRD entries + DECISIONS ADR additions;
  control-plane pivot banner added to top of docs/PRD.md (pointing
  at docs/CONTROL_PLANE_PRD.md which lands in next commit)

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

crates/storaged/src/append_log.rs

@@ -18,7 +18,7 @@
 ///   to small JSONL events.
 ///
 /// Storage layout:
-/// ```
+/// ```text
 /// {prefix}/
 ///   batch_0001776319628000123.jsonl
 ///   batch_0001776319745987654.jsonl
@@ -221,15 +221,15 @@ pub struct CompactStats {
     pub new_key: Option<String>,
 }
 
-// Proactively flush on drop, best-effort.
-// We can't `.await` in Drop; we spawn the flush on the tokio runtime if one
-// is available. If the runtime is already shutting down the flush is lost —
-// acceptable for these observability journals, which are hints not records.
+// Log unflushed-buffer size on drop. We can't `.await` from a sync `Drop`,
+// so a real flush isn't possible here — callers are responsible for calling
+// `.flush()` before dropping if durability matters. These journals are
+// observability hints; a few lost buffered events at shutdown are
+// acceptable per ADR-018.
 impl Drop for AppendLog {
     fn drop(&mut self) {
         let buf_len = self.buffer.try_lock().map(|b| b.len()).unwrap_or(0);
         if buf_len == 0 { return; }
-        // Can't spawn from sync Drop on every runtime shape; log + move on.
         tracing::debug!(
             "append_log '{}' dropping with {} unflushed events",
             self.prefix, buf_len,
@@ -237,3 +237,94 @@ impl Drop for AppendLog {
     }
 }
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use object_store::memory::InMemory;
+
+    fn mk(threshold: usize) -> AppendLog {
+        AppendLog::new(Arc::new(InMemory::new()), "prefix")
+            .with_flush_threshold(threshold)
+    }
+
+    #[tokio::test]
+    async fn append_stays_buffered_below_threshold() {
+        let log = mk(5);
+        log.append(b"one".to_vec()).await.unwrap();
+        log.append(b"two".to_vec()).await.unwrap();
+        assert_eq!(log.file_count().await.unwrap(), 0, "no files until threshold");
+        let all = log.read_all().await.unwrap();
+        assert_eq!(all, vec![b"one".to_vec(), b"two".to_vec()],
+            "read_all surfaces unflushed buffer");
+    }
+
+    #[tokio::test]
+    async fn append_auto_flushes_on_threshold() {
+        let log = mk(3);
+        for i in 0..3 {
+            log.append(format!("evt{i}").into_bytes()).await.unwrap();
+        }
+        assert_eq!(log.file_count().await.unwrap(), 1, "threshold triggered one flush");
+
+        // A fourth append stays buffered until the next threshold.
+        log.append(b"evt3".to_vec()).await.unwrap();
+        assert_eq!(log.file_count().await.unwrap(), 1, "below threshold again");
+    }
+
+    #[tokio::test]
+    async fn flush_empty_is_noop() {
+        let log = mk(32);
+        log.flush().await.unwrap();
+        log.flush().await.unwrap();
+        assert_eq!(log.file_count().await.unwrap(), 0);
+    }
+
+    #[tokio::test]
+    async fn read_all_orders_events_across_flushes() {
+        let log = mk(1); // flush-on-every-append
+        for i in 0..5 {
+            log.append(format!("e{i}").into_bytes()).await.unwrap();
+            // Spread writes out so timestamps sort strictly.
+            tokio::time::sleep(std::time::Duration::from_millis(2)).await;
+        }
+        let all = log.read_all().await.unwrap();
+        let strs: Vec<String> = all.into_iter()
+            .map(|v| String::from_utf8(v).unwrap())
+            .collect();
+        assert_eq!(strs, vec!["e0", "e1", "e2", "e3", "e4"],
+            "lex sort of batch keys == chronological event order");
+    }
+
+    #[tokio::test]
+    async fn compact_merges_multiple_files_into_one() {
+        let log = mk(1); // force file-per-append
+        for i in 0..4 {
+            log.append(format!("e{i}").into_bytes()).await.unwrap();
+            tokio::time::sleep(std::time::Duration::from_millis(2)).await;
+        }
+        assert_eq!(log.file_count().await.unwrap(), 4);
+
+        let stats = log.compact().await.unwrap();
+        assert_eq!(stats.merged_files, 4);
+        assert_eq!(stats.events, 4);
+        assert!(stats.new_key.is_some());
+
+        assert_eq!(log.file_count().await.unwrap(), 1, "originals deleted, 1 survivor");
+        let all = log.read_all().await.unwrap();
+        assert_eq!(all.len(), 4, "no events lost in compaction");
+    }
+
+    #[tokio::test]
+    async fn compact_with_single_file_is_noop() {
+        let log = mk(1);
+        log.append(b"only".to_vec()).await.unwrap();
+        assert_eq!(log.file_count().await.unwrap(), 1);
+
+        let stats = log.compact().await.unwrap();
+        assert_eq!(stats.merged_files, 1);
+        assert_eq!(stats.events, 0, "nothing to consolidate");
+        assert!(stats.new_key.is_none(), "no new file written");
+        assert_eq!(log.file_count().await.unwrap(), 1, "original untouched");
+    }
+}
+