import "replace" wipes KV but leaves search indices stale

[abhinav-m22]

After a replace-import, search returns memories that were just deleted and misses everything just imported, until a server restart.

• mem::import with strategy: "replace" deletes existing data across every namespace in src/functions/export-import.ts: observations (L274), memories (L279), and the rest
• But the file never touches the search indices: no getSearchIndex().remove(), vectorIndexRemove(), or rebuildIndex() anywhere
• After the wipe, BM25 and vector still hold the old entries
• The freshly imported data never gets indexed
• smart-search returns ghosts of deleted records and misses the imported ones for the whole process lifetime; only a restart fixes it

Fix

• Call rebuildIndex(kv) (exported from search.ts) at the end of import. It clears both indices and repopulates from KV, which is exactly the right post-import state