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/convert.go

@@ -0,0 +1,101 @@
+package sandbox
+
+import (
+	"fmt"
+
+	"go.starlark.net/starlark"
+)
+
+// GoToStarlark converts a Go value (typically from JSON unmarshal) to a
+// starlark.Value.  Handles nil, bool, int, int64, float64, string,
+// map[string]any, []any, and their interface{} equivalents.  Unknown
+// types are stringified.
+func GoToStarlark(v any) starlark.Value {
+	switch val := v.(type) {
+	case nil:
+		return starlark.None
+	case bool:
+		return starlark.Bool(val)
+	case int:
+		return starlark.MakeInt(val)
+	case int64:
+		return starlark.MakeInt64(val)
+	case float64:
+		if val == float64(int64(val)) {
+			return starlark.MakeInt64(int64(val))
+		}
+		return starlark.Float(val)
+	case string:
+		return starlark.String(val)
+	case map[string]any:
+		return MapToDict(val)
+	case []any:
+		elems := make([]starlark.Value, len(val))
+		for i, e := range val {
+			elems[i] = GoToStarlark(e)
+		}
+		return starlark.NewList(elems)
+	default:
+		return starlark.String(fmt.Sprintf("%v", val))
+	}
+}
+
+// StarlarkToGo converts a starlark.Value to a Go value suitable for
+// JSON serialization.  Handles None, Bool, Int, Float, String, List,
+// Dict, and Tuple.
+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 DictToMap(val)
+	case starlark.Tuple:
+		result := make([]any, len(val))
+		for i, e := range val {
+			result[i] = StarlarkToGo(e)
+		}
+		return result
+	default:
+		return v.String()
+	}
+}
+
+// DictToMap converts a *starlark.Dict to map[string]any.
+// Non-string keys are silently skipped.
+func DictToMap(d *starlark.Dict) map[string]any {
+	result := make(map[string]any, d.Len())
+	for _, item := range d.Items() {
+		k, ok := starlark.AsString(item[0])
+		if !ok {
+			continue
+		}
+		result[k] = StarlarkToGo(item[1])
+	}
+	return result
+}
+
+// MapToDict converts a map[string]any to *starlark.Dict.
+func MapToDict(m map[string]any) *starlark.Dict {
+	d := starlark.NewDict(len(m))
+	for k, v := range m {
+		_ = d.SetKey(starlark.String(k), GoToStarlark(v))
+	}
+	return d
+}