Remove stray .snap.new filtering from schema fixtures reader

Motivation:
- `codex-app-server-protocol` schema fixtures are not insta snapshots.
- Filtering `*.snap.new` is confusing and risks hiding real files.

What changed:
- Remove the `.snap.new` filename special case in `read_schema_fixture_tree`.

Refs: macOS Bazel schema fixture mismatch investigation

codex-rs/app-server-protocol/schema/json/v2/ModelListResponse.json

@@ -0,0 +1,94 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "Model": {
+      "properties": {
+        "defaultReasoningEffort": {
+          "$ref": "#/definitions/ReasoningEffort"
+        },
+        "description": {
+          "type": "string"
+        },
+        "displayName": {
+          "type": "string"
+        },
+        "id": {
+          "type": "string"
+        },
+        "isDefault": {
+          "type": "boolean"
+        },
+        "model": {
+          "type": "string"
+        },
+        "supportedReasoningEfforts": {
+          "items": {
+            "$ref": "#/definitions/ReasoningEffortOption"
+          },
+          "type": "array"
+        },
+        "supportsPersonality": {
+          "default": false,
+          "type": "boolean"
+        }
+      },
+      "required": [
+        "defaultReasoningEffort",
+        "description",
+        "displayName",
+        "id",
+        "isDefault",
+        "model",
+        "supportedReasoningEfforts"
+      ],
+      "type": "object"
+    },
+    "ReasoningEffort": {
+      "description": "See https://platform.openai.com/docs/guides/reasoning?api-mode=responses#get-started-with-reasoning",
+      "enum": [
+        "none",
+        "minimal",
+        "low",
+        "medium",
+        "high",
+        "xhigh"
+      ],
+      "type": "string"
+    },
+    "ReasoningEffortOption": {
+      "properties": {
+        "description": {
+          "type": "string"
+        },
+        "reasoningEffort": {
+          "$ref": "#/definitions/ReasoningEffort"
+        }
+      },
+      "required": [
+        "description",
+        "reasoningEffort"
+      ],
+      "type": "object"
+    }
+  },
+  "properties": {
+    "data": {
+      "items": {
+        "$ref": "#/definitions/Model"
+      },
+      "type": "array"
+    },
+    "nextCursor": {
+      "description": "Opaque cursor to pass to the next call to continue after the last item. If None, there are no more items to return.",
+      "type": [
+        "string",
+        "null"
+      ]
+    }
+  },
+  "required": [
+    "data"
+  ],
+  "title": "ModelListResponse",
+  "type": "object"
+}