(core) Floating formula editor

Summary:
Adding a way to detach an editor. Initially only implemented for the formula editor, includes redesign for the AI part.
- Initially, the detached editor is tight with the formula assistant and both are behind GRIST_FORMULA_ASSISTANT flag, but this can be relaxed
later on, as the detached editor can be used on its own.

- Detached editor is only supported in regular fields and on the creator panel. It is not supported yet for conditional styles, due to preview limitations.
- Old code for the assistant was removed completely, as it was only a temporary solution, but the AI conversation part was copied to the new one.
- Prompting was not modified in this diff, it will be included in the follow-up with more test cases.

Test Plan: Added only new tests; existing tests should pass.

Reviewers: JakubSerafin

Reviewed By: JakubSerafin

Differential Revision: https://phab.getgrist.com/D3863

app/client/models/entities/ColumnRec.ts

@@ -200,7 +200,11 @@ export interface ChatMessage {
   /**
    * The formula returned from the AI. It is only set when the sender is the AI.
    */
-  formula?: string;
+  formula?: string|null;
+  /**
+   * Suggested actions returned from the AI.
+   */
+  action?: any;
 }
 
 /**

app/client/models/entities/ViewFieldRec.ts

@@ -135,9 +135,26 @@ export function createViewFieldRec(this: ViewFieldRec, docModel: DocModel): void
   // CSS class to add to formula cells, incl. to show that we are editing this field's formula.
   this.formulaCssClass = ko.pureComputed<string|null>(() => {
     const col = this.column();
-    return this.column().isTransforming() ? "transform_field" :
-      (this.editingFormula() ? "formula_field_edit" :
-        (col.isFormula() && col.formula() !== "" ? "formula_field" : null));
+
+    // If the current column is transforming, assign the CSS class "transform_field"
+    if (col.isTransforming()) {
+      if ( col.origCol().isFormula() && col.origCol().formula() !== "") {
+        return "transform_field formula_field";
+      }
+      return "transform_field";
+    }
+    // If the column is not transforming but a formula is being edited
+    else if (this.editingFormula()) {
+      return "formula_field_edit";
+    }
+    // If a formula exists and it is not empty
+    else if (col.isFormula() && col.formula() !== "") {
+      return "formula_field";
+    }
+    // If none of the above conditions are met, assign null
+    else {
+      return null;
+    }
   });
 
   // The fields's display column