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/handlers/workflow_hooks.go

@@ -78,7 +78,7 @@ func FireOnAdvanceHook(
 	// Parse stage_data into Starlark dict
 	var dataMap map[string]interface{}
 	if json.Unmarshal(stageData, &dataMap) == nil {
-		_ = ctxDict.SetKey(starlark.String("stage_data"), jsonToStarlark(dataMap))
+		_ = ctxDict.SetKey(starlark.String("stage_data"), sandbox.GoToStarlark(dataMap))
 	} else {
 		_ = ctxDict.SetKey(starlark.String("stage_data"), starlark.NewDict(0))
 	}
@@ -117,7 +117,7 @@ func parseOnAdvanceResult(val starlark.Value) *OnAdvanceResult {
 	// Check for enriched stage_data
 	if sdVal, found, _ := d.Get(starlark.String("stage_data")); found {
 		if sd, ok := sdVal.(*starlark.Dict); ok {
-			goMap := starlarkDictToMap(sd)
+			goMap := sandbox.DictToMap(sd)
 			if data, err := json.Marshal(goMap); err == nil {
 				result.EnrichedData = data
 				return result
@@ -128,44 +128,3 @@ func parseOnAdvanceResult(val starlark.Value) *OnAdvanceResult {
 	return nil
 }
 
-// starlarkDictToMap converts a Starlark dict to a Go map.
-func starlarkDictToMap(d *starlark.Dict) map[string]any {
-	result := make(map[string]any, d.Len())
-	for _, item := range d.Items() {
-		k, ok := item[0].(starlark.String)
-		if !ok {
-			continue
-		}
-		result[string(k)] = starlarkToGo(item[1])
-	}
-	return result
-}
-
-// starlarkToGo converts a Starlark value to a Go value.
-func starlarkToGo(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.List:
-		result := make([]any, val.Len())
-		for i := 0; i < val.Len(); i++ {
-			result[i] = starlarkToGo(val.Index(i))
-		}
-		return result
-	case *starlark.Dict:
-		return starlarkDictToMap(val)
-	default:
-		return v.String()
-	}
-}