fix(sf): drop embedding row when memory is superseded

supersedeMemory soft-deleted via superseded_by but left the
memory_embeddings row in place. loadAllEmbeddings already filters
by superseded_by IS NULL, so the orphaned row is harmless functionally
— but it wastes storage, complicates manual SQL audits, and is
inconsistent with updateMemoryContent (which already invalidates the
embedding via 7bec2dc2d).

Best-effort delete; supersede still succeeds even if the embedding
delete raises. Symmetric with the update path.

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

src/resources/extensions/sf/memory-store.ts

@@ -343,12 +343,22 @@ export function reinforceMemory(id: string): boolean {
 
 /**
  * Mark a memory as superseded by another.
+ *
+ * Drops the superseded memory's embedding row too: loadAllEmbeddings()
+ * already filters by superseded_by IS NULL, so the row was dead weight
+ * — keeping it would just waste storage and confuse manual SQL audits.
+ * Best-effort: a missing/failed delete doesn't block the supersede.
  */
 export function supersedeMemory(oldId: string, newId: string): boolean {
 	if (!isDbAvailable()) return false;
 
 	try {
 		supersedeMemoryRow(oldId, newId, new Date().toISOString());
+		try {
+			deleteMemoryEmbedding(oldId);
+		} catch {
+			// Orphaned embedding rows are harmless; supersede still succeeded.
+		}
 		return true;
 	} catch {
 		return false;