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/v1/InitializeParams.json

@@ -0,0 +1,36 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "ClientInfo": {
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "title": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "version": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "name",
+        "version"
+      ],
+      "type": "object"
+    }
+  },
+  "properties": {
+    "clientInfo": {
+      "$ref": "#/definitions/ClientInfo"
+    }
+  },
+  "required": [
+    "clientInfo"
+  ],
+  "title": "InitializeParams",
+  "type": "object"
+}