Editor: cleaner transform-scaffold insertion

Insert the empty transform array inline (transform: []) instead of a multi-line
block, and pass adjustWhitespace:false to Monaco's snippet engine so it stops
re-basing the explicit indentation. The multi-line form left the closing bracket
under-indented and a stray blank line; the inline form lands cleanly indented as
the view's first property, with the first step filling it in place.

src/app/services/spec-transform-scaffold.ts

@@ -54,14 +54,16 @@ const COMMON_STEP_IDS = ['filter', 'aggregate', 'calculate', 'bin', 'timeUnit']
 
 /** Monaco's snippet contribution — the public entry to insert a `${n:…}` template with tab stops. */
 interface SnippetInserter extends monaco.editor.IEditorContribution {
-  insert(template: string): void;
+  insert(template: string, opts?: { adjustWhitespace?: boolean }): void;
 }
 
 /**
  * Insert a snippet template at `offset` through Monaco's snippet engine, so its
  * `${n:default}` tab stops become a live, Tab-through session. Places the cursor
- * first (the controller inserts at the selection). No-op if the contribution is
+ * first (the controller inserts at the selection). `adjustWhitespace: false` keeps
- * absent (it ships in `edcore.main`, so this is just defensive).
+ * the engine from re-basing our explicit indentation to the insertion line's — it
+ * otherwise leaves a multi-line block's closing bracket under-indented. No-op if the
+ * contribution is absent (it ships in `edcore.main`, so this is just defensive).
  */
 function insertSnippetAt(
   editor: monaco.editor.IStandaloneCodeEditor,
@@ -72,7 +74,9 @@ function insertSnippetAt(
   if (!model) return;
   editor.setPosition(model.getPositionAt(offset));
   editor.focus();
-  editor.getContribution<SnippetInserter>('snippetController2')?.insert(template);
+  editor.getContribution<SnippetInserter>('snippetController2')?.insert(template, {
+    adjustWhitespace: false,
+  });
 }
 
 let registered = false;
@@ -156,11 +160,11 @@ function runAddStep(
 
 /**
  * Insert an empty `transform: []` as the view's first property and drop the cursor
- * inside it (a `$0` tab stop), so the per-step lenses appear next. Indented off the
+ * between its brackets (`$0`), so the per-step lenses appear next and the first step
- * view line's own nesting, and separated from the next property with a comma only
+ * fills the array in place. The array is written **inline** — no interior newlines for
- * when one follows — a view with no other key (a bare `{}`) takes none, so the result
+ * the snippet engine to re-base — so it lands cleanly indented off the view line's own
- * stays valid JSON. The snippet engine precludes a reformat, so the indent is a best
+ * nesting. Separated from the following property with a comma only when one follows (a
- * effort the next document format tidies.
+ * view with no other key takes none), so the result stays valid JSON.
  */
 function runAddTransform(editor: monaco.editor.IStandaloneCodeEditor, viewOffset: number): void {
   const model = editor.getModel();
@@ -176,13 +180,8 @@ function runAddTransform(editor: monaco.editor.IStandaloneCodeEditor, viewOffset
   const braceLine = model.getPositionAt(brace).lineNumber;
   const baseIndent = /^\s*/.exec(model.getLineContent(braceLine))?.[0].length ?? 0;
   const indent = ' '.repeat(baseIndent + tab);
-  const inner = ' '.repeat(tab);
   const trail = neighbour(text, brace + 1, 1) === '}' ? '' : ',';
-  insertSnippetAt(
+  insertSnippetAt(editor, brace + 1, `\n${indent}"transform": [$0]${trail}`);
-    editor,
-    brace + 1,
-    `\n${indent}"transform": [\n${indent}${inner}$0\n${indent}]${trail}`,
-  );
 }
 
 /**