fix(ui): per-field sub-schema for escape-hatch Monaco editors + dispose guard (#261)

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/ParameterValueForm.razor

@@ -53,12 +53,6 @@ else
     private InboundApiSchema? _rootSchema;
     private string? _parsedFor;
 
-    // The resolved root schema serialized back to a JSON Schema string (with every
-    // {"$ref":"lib:Name"} inlined). Fed to the raw-JSON escape-hatch Monaco editor
-    // so Monaco's built-in JSON language offers schema-driven hover + completion on
-    // the entered JSON. Computed once per parse alongside the resolved schema.
-    private string? _resolvedSchemaJson;
-
     // Raw text and per-field parse/validation errors keyed by canonical PATH
     // (e.g. "order.id", "tags[0]") so nested inputs each carry their own state.
     private readonly Dictionary<string, string> _rawText = new();
@@ -76,9 +70,22 @@ else
         _shapes = ScriptParameterNames.ParseShapes(ParameterDefinitions);
         _rootSchema = await ParseRootAsync();
         _topLevelFields = _rootSchema?.Type == "object" ? _rootSchema.Fields : Array.Empty<InboundApiSchemaField>();
-        _resolvedSchemaJson = _rootSchema is null ? null : ToJsonSchema(_rootSchema);
     }
 
+    /// <summary>
+    /// Serializes the escape-hatch FIELD's own (resolved) sub-schema to a JSON
+    /// Schema string for that field's Monaco editor — NOT the whole root object
+    /// schema. So a field's raw-JSON editor validates/completes against just that
+    /// field's portion of the type, not the entire object. Any
+    /// <c>{"$ref":"lib:Name"}</c> the parse already inlined is emitted as its
+    /// resolved shape; a node whose ref could NOT be resolved (Type
+    /// <c>"ref"</c>) — or any unknown type — has no derivable sub-schema and
+    /// collapses to a permissive <c>{}</c>, so the editor still validates
+    /// well-formed JSON without false errors. Cheap and on-demand: only the rare
+    /// escape-hatch nodes pay for it, and only at render time.
+    /// </summary>
+    private static string FieldSchemaJson(InboundApiSchema fieldSchema) => ToJsonSchema(fieldSchema);
+
     /// <summary>
     /// Serializes a (resolved) <see cref="InboundApiSchema"/> back to a JSON Schema
     /// string for the escape-hatch Monaco editor. Any <c>{"$ref":"lib:Name"}</c> the
@@ -250,7 +257,7 @@ else
             default: // unresolved $ref / unknown — raw-JSON escape hatch (Monaco).
                 <div class="param-json-editor" data-path="@path">
                     <MonacoEditor Language="json" Height="120px" ShowToolbar="false"
-                                  JsonSchema="@_resolvedSchemaJson"
+                                  JsonSchema="@FieldSchemaJson(schema)"
                                   Value="@AsRaw(path)"
                                   ValueChanged="@(v => SetJson(path, v))" />
                 </div>