Add offset plane point-and-click user flow (#4552)

* Add a code mod for offset plane

* Add support for default plane selections to our `otherSelections` object

* Make availableVars work without a selection range
(because default planes don't have one)

* Make default planes selectable in cmdbar even if AST is empty

* Add offset plane command and activate in toolbar

* Avoid unnecessary error when sketching on offset plane by returning early

* Add supporting test features for offset plane E2E test

* Add WIP E2E test for offset plane
Struggling to get local electron test suite running properly

* Typos

* Lints

* Fix test by making it a web-based one:
I couldn't use the cmdBar fixture with an electron test for some reason.

* Update src/lib/commandBarConfigs/modelingCommandConfig.ts

* Update src/machines/modelingMachine.ts

* Revert changes to `homePageFixture`, as they were unused

* @Irev-Dev feedback: convert action to actor, fix machine layout

* Update plane icon to be not dashed, follow conventions closer

src/lang/modifyAst.ts

@@ -527,6 +527,45 @@ export function sketchOnExtrudedFace(
   }
 }
 
+/**
+ * Append an offset plane to the AST
+ */
+export function addOffsetPlane({
+  node,
+  defaultPlane,
+  offset,
+}: {
+  node: Node<Program>
+  defaultPlane: DefaultPlaneStr
+  offset: Expr
+}): { modifiedAst: Node<Program>; pathToNode: PathToNode } {
+  const modifiedAst = structuredClone(node)
+  const newPlaneName = findUniqueName(node, KCL_DEFAULT_CONSTANT_PREFIXES.PLANE)
+
+  const newPlane = createVariableDeclaration(
+    newPlaneName,
+    createCallExpressionStdLib('offsetPlane', [
+      createLiteral(defaultPlane.toUpperCase()),
+      offset,
+    ])
+  )
+
+  modifiedAst.body.push(newPlane)
+  const pathToNode: PathToNode = [
+    ['body', ''],
+    [modifiedAst.body.length - 1, 'index'],
+    ['declarations', 'VariableDeclaration'],
+    ['0', 'index'],
+    ['init', 'VariableDeclarator'],
+    ['arguments', 'CallExpression'],
+    [0, 'index'],
+  ]
+  return {
+    modifiedAst,
+    pathToNode,
+  }
+}
+
 /**
  * Modify the AST to create a new sketch using the variable declaration
  * of an offset plane. The new sketch just has to come after the offset