Add CI workflow for validating C++ API snapshot (#56042)

Summary:

Adds CI workflow for validating whether the current C++ API snapshot is equivalent with the generated one.

Changelog:
[Internal]

Differential Revision: D95963515

Author: coado

.github/workflows/validate-cxx-api-snapshots.yml

@@ -0,0 +1,48 @@
+name: Validate C++ API Snapshots
+
+on:
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - "packages/react-native/ReactCommon/**"
+      - "packages/react-native/ReactAndroid/**"
+      - "packages/react-native/React/**"
+      - "packages/react-native/ReactApple/**"
+      - "packages/react-native/Libraries/**"
+      - "scripts/cxx-api/**"
+  push:
+    branches:
+      - main
+      - "*-stable"
+    paths:
+      - "packages/react-native/ReactCommon/**"
+      - "packages/react-native/ReactAndroid/**"
+      - "packages/react-native/React/**"
+      - "packages/react-native/ReactApple/**"
+      - "packages/react-native/Libraries/**"
+      - "scripts/cxx-api/**"
+
+jobs:
+  validate_cxx_api_snapshots:
+    runs-on: ubuntu-latest
+    if: github.repository == 'facebook/react-native'
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+      - name: Setup node.js
+        uses: ./.github/actions/setup-node
+      - name: Run yarn
+        uses: ./.github/actions/yarn-install
+      - name: Install Doxygen
+        shell: bash
+        run: sudo apt-get update && sudo apt-get install -y doxygen
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - name: Install Python dependencies
+        shell: bash
+        run: pip install doxmlparser natsort pyyaml
+      - name: Validate C++ API snapshots
+        shell: bash
+        run: yarn cxx-api-validate

packages/react-native/ReactCommon/react/renderer/debug/DebugStringConvertible.h

@@ -20,7 +20,7 @@ namespace facebook::react {
 
 #if RN_DEBUG_STRING_CONVERTIBLE
 
-class DebugStringConvertible;
+// class DebugStringConvertible;
 
 using SharedDebugStringConvertible = std::shared_ptr<const DebugStringConvertible>;
 using SharedDebugStringConvertibleList = std::vector<SharedDebugStringConvertible>;