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/Cargo.lock

@@ -1126,12 +1126,15 @@ dependencies = [
  "clap",
  "codex-protocol",
  "codex-utils-absolute-path",
+ "codex-utils-cargo-bin",
  "mcp-types",
  "pretty_assertions",
  "schemars 0.8.22",
  "serde",
  "serde_json",
+ "similar",
  "strum_macros 0.27.2",
+ "tempfile",
  "thiserror 2.0.17",
  "ts-rs",
  "uuid",