feat(chunking): add AST-aware code chunking for Go, Python, TypeScript

- [x] Add language-specific chunkers with AST parsing (Go, Python, TypeScript)
- [x] Implement chunking manager to dispatch files to appropriate chunkers
- [x] Integrate code chunks into vector sync for semantic search
- [x] Add tree-sitter dependency for Python/TypeScript parsing
- [x] Reorder struct fields for consistency across codebase
- [x] Rename error variables to follow Go conventions (err → unmarshalErr, etc.)
- [x] Add code chunk metadata to vector documents (language, symbol name, line ranges)
- [x] Update worker service to initialize chunking pipeline with all three languages

internal/worker/sse/broadcaster.go

@@ -19,10 +19,10 @@ const (
 
 // Client represents a connected SSE client.
 type Client struct {
-	ID      string
 	Writer  http.ResponseWriter
 	Flusher http.Flusher
 	Done    chan struct{}
+	ID      string
 }
 
 // Broadcaster manages SSE client connections and message broadcasting.

internal/worker/sse/broadcaster_test.go

@@ -256,8 +256,8 @@ func TestHandleSSE(t *testing.T) {
 // TestBroadcastJSON tests broadcasting various JSON types.
 func TestBroadcastJSON(t *testing.T) {
 	tests := []struct {
-		name    string
 		data    interface{}
+		name    string
 		wantErr bool
 	}{
 		{