Feat v0.9.2 Starlark converter consolidation + snapshot cleanup (#75)

Consolidate duplicate Go↔Starlark converters into sandbox/convert.go
and snapshot parsers into models/snapshot.go. Standardize snapshot
creation on wrapped format. Net -393 lines across 21 files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/sandbox/realtime_module.go

@@ -83,7 +83,7 @@ func realtimePublish(ctx context.Context, bus *events.Bus, packageID string) fun
 				if k == "_pkg" {
 					continue // reserved field
 				}
-				payload[k] = starlarkToGoVal(item[1])
+				payload[k] = StarlarkToGo(item[1])
 			}
 		}
 
@@ -108,46 +108,3 @@ func realtimePublish(ctx context.Context, bus *events.Bus, packageID string) fun
 	}
 }
 
-// starlarkToGoVal converts a Starlark value to a Go value for JSON marshaling.
-func starlarkToGoVal(v starlark.Value) any {
-	switch val := v.(type) {
-	case starlark.NoneType:
-		return nil
-	case starlark.Bool:
-		return bool(val)
-	case starlark.Int:
-		if i, ok := val.Int64(); ok {
-			return i
-		}
-		return val.String()
-	case starlark.Float:
-		return float64(val)
-	case starlark.String:
-		return string(val)
-	case *starlark.Dict:
-		m := make(map[string]any, val.Len())
-		for _, item := range val.Items() {
-			k, ok := starlark.AsString(item[0])
-			if !ok {
-				k = item[0].String()
-			}
-			m[k] = starlarkToGoVal(item[1])
-		}
-		return m
-	case *starlark.List:
-		n := val.Len()
-		s := make([]any, n)
-		for i := 0; i < n; i++ {
-			s[i] = starlarkToGoVal(val.Index(i))
-		}
-		return s
-	case starlark.Tuple:
-		s := make([]any, len(val))
-		for i, v := range val {
-			s[i] = starlarkToGoVal(v)
-		}
-		return s
-	default:
-		return v.String()
-	}
-}