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/db/gorm/session_store.go

@@ -4,6 +4,7 @@ package gorm
 import (
 	"context"
 	"database/sql"
+	"fmt"
 	"time"
 
 	"gorm.io/gorm"
@@ -67,10 +68,12 @@ func (s *SessionStore) CreateSDKSession(ctx context.Context, claudeSessionID, pr
 			if userPrompt != "" {
 				updates["user_prompt"] = userPrompt
 			}
-			s.db.WithContext(ctx).
+			if err := s.db.WithContext(ctx).
 				Model(&SDKSession{}).
 				Where("claude_session_id = ?", claudeSessionID).
-				Updates(updates)
+				Updates(updates).Error; err != nil {
+				return 0, fmt.Errorf("failed to update session: %w", err)
+			}
 		}
 
 		// Fetch existing session

internal/mcp/server.go

@@ -164,7 +164,7 @@ func (s *Server) handleToolsList(req *Request) *Response {
 	tools := []Tool{
 		{
 			Name:        "search",
-			Description: "Unified search across all memory types (observations, sessions, and user prompts) using vector-first semantic search (ChromaDB).",
+			Description: "Unified search across all memory types (observations, sessions, and user prompts) using vector-first semantic search (sqlite-vec).",
 			InputSchema: map[string]any{
 				"type": "object",
 				"properties": map[string]any{
@@ -599,7 +599,8 @@ func (s *Server) handleFindRelatedObservations(ctx context.Context, args json.Ra
 		return "", fmt.Errorf("id is required")
 	}
 
-	if params.MinConfidence == 0 {
+	// Use -1 as sentinel for "not provided" since 0.0 is a valid threshold
+	if params.MinConfidence < 0 {
 		params.MinConfidence = 0.5
 	}
 

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)