[core] Add CodSpeed C++ benchmarks for protobuf and main loop

Add automated benchmarks using Google Benchmark to prevent performance
regressions in the API protobuf encoding/decoding and core loop paths.

Benchmarks cover:
- Protobuf encode: SensorState, BinarySensorState, HelloResponse,
  LightState, DeviceInfoResponse (20 nested devices + 20 areas)
- Protobuf decode: HelloRequest, SwitchCommand, LightCommand
- Protobuf calculate_size and full calc+encode send path
- Varint parse/encode/size for various value ranges
- Scheduler call/next_schedule_in with idle and active timers
- Application loop component dispatch and blocking guard overhead

Infrastructure:
- Extract shared build logic from cpp_unit_test.py into test_helpers.py
- Add cpp_benchmark.py mirroring the unit test build pattern
- Support benchmark.yaml per component dir for declaring dependencies
- Add CodSpeed CI workflow triggered on api/core changes
- Fix ProtoMessage protected destructor on host platform

.github/workflows/ci-benchmarks.yml

@@ -0,0 +1,87 @@
+---
+name: CodSpeed Benchmarks
+
+on:
+  push:
+    branches: [dev]
+  pull_request:
+    paths:
+      - "esphome/components/api/**"
+      - "esphome/core/**"
+      - "tests/benchmarks/**"
+      - "script/cpp_benchmark.py"
+      - "script/test_helpers.py"
+      - ".github/workflows/ci-benchmarks.yml"
+  merge_group:
+
+permissions:
+  contents: read
+
+concurrency:
+  # yamllint disable-line rule:line-length
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+env:
+  DEFAULT_PYTHON: "3.11"
+
+jobs:
+  common:
+    name: Create common environment
+    runs-on: ubuntu-24.04
+    outputs:
+      cache-key: ${{ steps.cache-key.outputs.key }}
+    steps:
+      - name: Check out code from GitHub
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - name: Generate cache-key
+        id: cache-key
+        run: echo key="${{ hashFiles('requirements.txt', 'requirements_test.txt') }}" >> $GITHUB_OUTPUT
+      - name: Set up Python ${{ env.DEFAULT_PYTHON }}
+        id: python
+        uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
+        with:
+          python-version: ${{ env.DEFAULT_PYTHON }}
+      - name: Restore Python virtual environment
+        id: cache-venv
+        uses: actions/cache@cdf6c1fa76f9f475f3d7449005a359c84ca0f306 # v5.0.3
+        with:
+          path: venv
+          # yamllint disable-line rule:line-length
+          key: ${{ runner.os }}-${{ steps.python.outputs.python-version }}-venv-${{ steps.cache-key.outputs.key }}
+      - name: Create Python virtual environment
+        if: steps.cache-venv.outputs.cache-hit != 'true'
+        run: |
+          python -m venv venv
+          . venv/bin/activate
+          python --version
+          pip install -r requirements.txt -r requirements_test.txt
+          pip install -e .
+
+  benchmarks:
+    name: Run CodSpeed Benchmarks
+    runs-on: ubuntu-24.04
+    needs:
+      - common
+    steps:
+      - name: Check out code from GitHub
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - name: Restore Python
+        uses: ./.github/actions/restore-python
+        with:
+          python-version: ${{ env.DEFAULT_PYTHON }}
+          cache-key: ${{ needs.common.outputs.cache-key }}
+
+      - name: Build benchmarks
+        id: build
+        run: |
+          . venv/bin/activate
+          BINARY=$(script/cpp_benchmark.py --all --build-only 2>&1 | tail -1)
+          echo "binary=$BINARY" >> $GITHUB_OUTPUT
+
+      - name: Run CodSpeed benchmarks
+        uses: CodSpeedHQ/action@v4
+        with:
+          run: ${{ steps.build.outputs.binary }}
+          token: ${{ secrets.CODSPEED_TOKEN }}