fix(hooks,db,mcp,worker): add type safety and error handling (#21)

- [x] Add type checking and error handling for JSON type assertions in user-prompt hook
- [x] Add error handling for session update query in CreateSDKSession
- [x] Update MCP tool description to reference sqlite-vec instead of ChromaDB
- [x] Fix MinConfidence sentinel value check from 0 to -1
- [x] Pass project parameter to vector search filter in handleSearchByPrompt
- [x] Return empty map instead of nil for successful responses without JSON body

internal/worker/handlers.go

@@ -774,7 +774,7 @@ func (s *Service) handleSearchByPrompt(w http.ResponseWriter, r *http.Request) {
 
 	// Try vector search first if available
 	if s.vectorClient != nil && s.vectorClient.IsConnected() {
-		where := sqlitevec.BuildWhereFilter(sqlitevec.DocTypeObservation, "")
+		where := sqlitevec.BuildWhereFilter(sqlitevec.DocTypeObservation, project)
 
 		// Search with each expanded query and merge results
 		allVectorResults := make([]sqlitevec.QueryResult, 0)