Editor: CodeLens + completion to scaffold Vega-Lite params; shared snippet core

src/app/components/SpecEditor.tsx

@@ -54,6 +54,10 @@ import {
   configureSpecTransformScaffold,
   installSpecTransformScaffoldCodeLens,
 } from '../services/spec-transform-scaffold';
+import {
+  configureSpecParamScaffold,
+  installSpecParamScaffoldCodeLens,
+} from '../services/spec-param-scaffold';
 import { runExtract } from '../services/extract-action';
 import { useAppStore } from '../stores/AppStore';
 import { confirm } from '../stores/ConfirmStore';
@@ -179,6 +183,8 @@ configureSpecDatasetHints();
 configureSpecExpressionHints();
 // Register the data-transform step-scaffold completion once (docs/architecture/08).
 configureSpecTransformScaffold();
+// Register the parameter-scaffold completion once (docs/architecture/08).
+configureSpecParamScaffold();
 
 /** The two spec↔config operations, surfaced as an overflow menu (council:
  *  Carbon menu-buttons — overflow for additional options under space
@@ -466,6 +472,10 @@ export function SpecEditor() {
     // — per editor for the same reason: its commands drive this editor's snippet edit.
     const scaffoldLensSub = installSpecTransformScaffoldCodeLens(editor);
 
+    // Cursor-aware parameter scaffold CodeLens (＋ slider / ＋ point …) — per editor,
+    // its command splices the seeded param into this editor via the snippet engine.
+    const paramScaffoldLensSub = installSpecParamScaffoldCodeLens(editor);
+
     // Validate Vega expressions in the draft and squiggle the invalid ones — per
     // editor, because it writes markers to this model (docs/architecture/08).
     // Debounced internally; recomputes on edit and on a draft↔published toggle.
@@ -483,6 +493,7 @@ export function SpecEditor() {
       transformActionsSub.dispose();
       codeLensSub.dispose();
       scaffoldLensSub.dispose();
+      paramScaffoldLensSub.dispose();
       exprMarkersSub.dispose();
       editor.dispose();
       editorRef.current = null;