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/ThreadStartParams.json

@@ -0,0 +1,137 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "AskForApproval": {
+      "enum": [
+        "untrusted",
+        "on-failure",
+        "on-request",
+        "never"
+      ],
+      "type": "string"
+    },
+    "DynamicToolSpec": {
+      "properties": {
+        "description": {
+          "type": "string"
+        },
+        "inputSchema": true,
+        "name": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "description",
+        "inputSchema",
+        "name"
+      ],
+      "type": "object"
+    },
+    "Personality": {
+      "enum": [
+        "friendly",
+        "pragmatic"
+      ],
+      "type": "string"
+    },
+    "SandboxMode": {
+      "enum": [
+        "read-only",
+        "workspace-write",
+        "danger-full-access"
+      ],
+      "type": "string"
+    }
+  },
+  "properties": {
+    "approvalPolicy": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/AskForApproval"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "baseInstructions": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "config": {
+      "additionalProperties": true,
+      "type": [
+        "object",
+        "null"
+      ]
+    },
+    "cwd": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "developerInstructions": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "dynamicTools": {
+      "items": {
+        "$ref": "#/definitions/DynamicToolSpec"
+      },
+      "type": [
+        "array",
+        "null"
+      ]
+    },
+    "ephemeral": {
+      "type": [
+        "boolean",
+        "null"
+      ]
+    },
+    "experimentalRawEvents": {
+      "default": false,
+      "description": "If true, opt into emitting raw response items on the event stream.\n\nThis is for internal use only (e.g. Codex Cloud). (TODO): Figure out a better way to categorize internal / experimental events & protocols.",
+      "type": "boolean"
+    },
+    "model": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "modelProvider": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "personality": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/Personality"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "sandbox": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/SandboxMode"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    }
+  },
+  "title": "ThreadStartParams",
+  "type": "object"
+}