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/DynamicToolCallParams.json

@@ -0,0 +1,27 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "arguments": true,
+    "callId": {
+      "type": "string"
+    },
+    "threadId": {
+      "type": "string"
+    },
+    "tool": {
+      "type": "string"
+    },
+    "turnId": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "arguments",
+    "callId",
+    "threadId",
+    "tool",
+    "turnId"
+  ],
+  "title": "DynamicToolCallParams",
+  "type": "object"
+}