Type ascription produces two incompatible fields (#7355)

# Symptoms

This code produces a big ugly confusing error in the frontend, see #7340.

# Root cause

I added a new test case, with an unknown type. In `ast.snap` under `body[0].declaration.init.ty` there two different `type` fields in the AST node for the type's name, and they have conflicting values Primitive and Identifier.

<img width="602" alt="Screenshot 2025-06-03 at 4 04 55 PM" src="https://github.com/user-attachments/assets/913a0fa0-3e8d-473f-bb64-003d44915be0" />

# Solution

Change the `enum PrimitiveType` variant from `Named(Node<Identifier>)` to `Named { name: Node<Identifier> }` so that the fields nest differently.

Now the error correctly points out to the user that the type `NotARealType` can't be found. Much better error message that shows the user the problem.

# Alternative solutions

Stop the duplicated JSON fields altogether. I tried this previously in https://github.com/KittyCAD/modeling-app/pull/4369 but it was very involved, and I didn't think it was worth it. Maybe I should reopen that PR and solve this properly.

Closes #7340

rust/kcl-lib/tests/ascription_unknown_type/artifact_commands.snap

@@ -0,0 +1,32 @@
+---
+source: kcl-lib/src/simulation_tests.rs
+description: Artifact commands ascription_unknown_type.kcl
+---
+[
+  {
+    "cmdId": "[uuid]",
+    "range": [],
+    "command": {
+      "type": "edge_lines_visible",
+      "hidden": false
+    }
+  },
+  {
+    "cmdId": "[uuid]",
+    "range": [],
+    "command": {
+      "type": "object_visible",
+      "object_id": "[uuid]",
+      "hidden": true
+    }
+  },
+  {
+    "cmdId": "[uuid]",
+    "range": [],
+    "command": {
+      "type": "object_visible",
+      "object_id": "[uuid]",
+      "hidden": true
+    }
+  }
+]

rust/kcl-lib/tests/ascription_unknown_type/artifact_graph_flowchart.snap

@@ -0,0 +1,6 @@
+---
+source: kcl-lib/src/simulation_tests.rs
+description: Artifact graph flowchart ascription_unknown_type.kcl
+extension: md
+snapshot_kind: binary
+---

rust/kcl-lib/tests/ascription_unknown_type/artifact_graph_flowchart.snap.md

@@ -0,0 +1,3 @@
+```mermaid
+flowchart LR
+```

rust/kcl-lib/tests/ascription_unknown_type/ast.snap

@@ -0,0 +1,67 @@
+---
+source: kcl-lib/src/simulation_tests.rs
+description: Result of parsing ascription_unknown_type.kcl
+---
+{
+  "Ok": {
+    "body": [
+      {
+        "commentStart": 0,
+        "declaration": {
+          "commentStart": 0,
+          "end": 0,
+          "id": {
+            "commentStart": 0,
+            "end": 0,
+            "name": "z",
+            "start": 0,
+            "type": "Identifier"
+          },
+          "init": {
+            "commentStart": 0,
+            "end": 0,
+            "expr": {
+              "commentStart": 0,
+              "end": 0,
+              "raw": "10",
+              "start": 0,
+              "type": "Literal",
+              "type": "Literal",
+              "value": {
+                "value": 10.0,
+                "suffix": "None"
+              }
+            },
+            "start": 0,
+            "ty": {
+              "commentStart": 0,
+              "end": 0,
+              "id": {
+                "commentStart": 0,
+                "end": 0,
+                "name": "NotARealType",
+                "start": 0,
+                "type": "Identifier"
+              },
+              "p_type": "Named",
+              "start": 0,
+              "type": "Primitive"
+            },
+            "type": "AscribedExpression",
+            "type": "AscribedExpression"
+          },
+          "start": 0,
+          "type": "VariableDeclarator"
+        },
+        "end": 0,
+        "kind": "const",
+        "start": 0,
+        "type": "VariableDeclaration",
+        "type": "VariableDeclaration"
+      }
+    ],
+    "commentStart": 0,
+    "end": 0,
+    "start": 0
+  }
+}

rust/kcl-lib/tests/ascription_unknown_type/execution_error.snap

@@ -0,0 +1,12 @@
+---
+source: kcl-lib/src/simulation_tests.rs
+description: Error from executing ascription_unknown_type.kcl
+---
+KCL Semantic error
+
+  × semantic: Unknown type: NotARealType
+   ╭────
+ 1 │ z = 10: NotARealType
+   ·     ─┬
+   ·      ╰── tests/ascription_unknown_type/input.kcl
+   ╰────

rust/kcl-lib/tests/ascription_unknown_type/input.kcl

@@ -0,0 +1 @@
+z = 10: NotARealType

rust/kcl-lib/tests/ascription_unknown_type/ops.snap

@@ -0,0 +1,5 @@
+---
+source: kcl-lib/src/simulation_tests.rs
+description: Operations executed ascription_unknown_type.kcl
+---
+[]

rust/kcl-lib/tests/ascription_unknown_type/unparsed.snap

@@ -0,0 +1,5 @@
+---
+source: kcl-lib/src/simulation_tests.rs
+description: Result of unparsing ascription_unknown_type.kcl
+---
+z = 10: NotARealType