Phase 26 — Mem0 upsert + Letta geo hot cache

Closes the two remaining 2026-era memory findings. Both are
optimizations per J's framing — not load-bearing, but good data
hygiene + future-proofing at scale.

MEM0 UPSERT (data hygiene):
Before: /seed always appended. A scenario re-running the same
operation on the same day wrote duplicate entries, inflating the
playbook corpus with near-identical rows.

Now: upsert_entry(new) inspects existing non-retired entries and
decides ADD / UPDATE / NOOP:
  ADD     → no matching (operation, day, city, state) tuple, append
  UPDATE  → match exists with different names → merge (union, stable
            order), refresh timestamp, keep original playbook_id so
            citations stay valid
  NOOP    → match exists with identical names → skip, return id

Day-granularity keying on timestamp YYYY-MM-DD means intraday
re-seeds dedup but tomorrow's same-operation is a fresh ADD. Retired
entries don't block new seeds — they're out of scope anyway.

Seed endpoint returns {outcome: {mode, playbook_id, merged_names?},
entries_after}. Append=false retains old replace-all semantics.

5 unit tests pass: first_seed_is_add, identical_reseed_is_noop,
same_day_different_names_updates_and_merges, different_day_same_op_is_add,
retired_entry_doesnt_block_new_seed.

Live verified: three successive seeds with (Alice), (Alice),
(Alice, Bob) left entry count unchanged at 1936 with merged names
{Alejandro, Lauren, Alice, Bob}. Previously would have been 3
appends.

LETTA GEO HOT CACHE (scale primitive):
Added geo_index: HashMap<(city_lower, state_upper), Vec<usize>>
alongside PlaybookMemoryState. Rebuilt on every mutation: set_entries,
retire_one, retire_on_schema_drift, upsert_entry, load_from_storage.

compute_boost_for_filtered_with_role now uses the index for O(1) geo
lookup instead of scanning all entries. At current scale (1.9K) the
scan was sub-ms; at 100K+ the scan becomes the dominant cost. The
hot cache future-proofs without adding an LRU abstraction.

Retired entries excluded from index; valid_until still checked on the
hot path since it can elapse between rebuilds.

Owns cloned PlaybookEntries in the geo_filtered vector so the state
read-lock is released before cosine scoring — avoids lock contention
on the scoring path.

Memory-findings progress: 5 of 5 shipped.
  ✓ Multi-strategy parallel retrieval (Phase 19 refinement)
  ✓ Input normalization + unified /memory/query (Phase 24 TS)
  ✓ Zep validity windows (Phase 25)
  ✓ Mem0 UPSERT (Phase 26 today)
  ✓ Letta geo hot cache (Phase 26 today)

All 18 playbook_memory tests pass.

crates/vectord/src/service.rs

@@ -2289,16 +2289,30 @@ async fn seed_playbook_memory(
         retirement_reason: None,
     };
 
-    let mut current = state.playbook_memory.snapshot().await;
+    // Phase 26 — when append=true (default), route through upsert so
+    // same-day re-seeds of the same operation merge instead of
+    // appending duplicates. When append=false, retain the old
+    // replace-all semantics for callers that want a hard reset.
     if req.append {
-        current.push(new_entry);
+        match state.playbook_memory.upsert_entry(new_entry).await {
+            Ok(outcome) => {
+                let entries_after = state.playbook_memory.entry_count().await;
+                Ok(Json(serde_json::json!({
+                    "outcome": outcome,
+                    "entries_after": entries_after,
+                })))
+            }
+            Err(e) => Err((StatusCode::INTERNAL_SERVER_ERROR, format!("upsert: {e}"))),
+        }
     } else {
-        current = vec![new_entry];
+        if let Err(e) = state.playbook_memory.set_entries(vec![new_entry]).await {
+            return Err((StatusCode::INTERNAL_SERVER_ERROR, format!("persist: {e}")));
+        }
+        Ok(Json(serde_json::json!({
+            "outcome": { "mode": "replaced", "playbook_id": pid },
+            "entries_after": state.playbook_memory.entry_count().await,
+        })))
     }
-    if let Err(e) = state.playbook_memory.set_entries(current).await {
-        return Err((StatusCode::INTERNAL_SERVER_ERROR, format!("persist: {e}")));
-    }
-    Ok(Json(serde_json::json!({ "playbook_id": pid, "entries_after": state.playbook_memory.entry_count().await })))
 }
 
 async fn rebuild_playbook_memory(