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/GetAccountParams.json

@@ -0,0 +1,12 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "refreshToken": {
+      "default": false,
+      "description": "When `true`, requests a proactive token refresh before returning.\n\nIn managed auth mode this triggers the normal refresh-token flow. In external auth mode this flag is ignored. Clients should refresh tokens themselves and call `account/login/start` with `chatgptAuthTokens`.",
+      "type": "boolean"
+    }
+  },
+  "title": "GetAccountParams",
+  "type": "object"
+}