Simplify the native dispatch and CI cache wiring

A cache-arduino8266 composite action mirrors cache-esp-idf (one key
resolver, dev-writes/PR-restores) and both jobs pin
ESPHOME_ARDUINO8266_PREFIX so YAML and Python agree on the path by
construction. esp32 provides the native_toolchain_module hook, so the
shared dispatcher never names a backend and the unclaimed-native raise
loses its esp-idf carve-out; the esp8266 decode and run_compile hooks
resolve through the same seam. run_compile resolves ccache once and
threads it to the generator, env, and idedata; the compdb rule names
follow the shared kinds; the pio-options warner inlines into the driver
and derives its consumed set from the core routing constant; the
per-toolchain CI narrowing shares one body; create_components_graph is
memoized per run; the decode rate-limit drops its math sentinel.

.github/actions/cache-arduino8266/action.yml

@@ -0,0 +1,36 @@
+name: Cache Arduino ESP8266
+description: >
+  Resolve the pinned Arduino core and xtensa toolchain versions and cache the
+  native ESP8266 install (~110 MB framework + toolchain; no ccache store, the
+  seed job saves before any compile runs). Callers must set env
+  ESPHOME_ARDUINO8266_PREFIX: ~/.esphome-arduino8266 and have the Python venv
+  already restored. Mirrors cache-esp-idf: only dev-branch pushes write the
+  shared cache, everything else restores.
+runs:
+  using: composite
+  steps:
+    - name: Resolve the native toolchain cache key
+      # The versions are pinned in code, not in a hashable file, so resolve
+      # them for the key (actions/cache never overwrites a key, so a bump
+      # must change it). Assignment form so errexit catches a resolver
+      # failure; a nested $(...) inside echo would silently yield a
+      # degenerate key.
+      id: version
+      shell: bash
+      run: |
+        . venv/bin/activate
+        key=$(python -c 'from esphome.components.esp8266 import RECOMMENDED_ARDUINO_FRAMEWORK_VERSION as f; from esphome.arduino8266.framework import TOOLCHAIN_VERSION as t; print(f"{f}-{t}")')
+        [ -n "$key" ] || exit 1
+        echo "key=$key" >> "$GITHUB_OUTPUT"
+    - name: Cache the native toolchain (write on dev)
+      if: github.ref == 'refs/heads/dev'
+      uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: ~/.esphome-arduino8266
+        key: ${{ runner.os }}-esp8266-native-${{ steps.version.outputs.key }}
+    - name: Restore the native toolchain (off dev)
+      if: github.ref != 'refs/heads/dev'
+      uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: ~/.esphome-arduino8266
+        key: ${{ runner.os }}-esp8266-native-${{ steps.version.outputs.key }}

.github/workflows/ci.yml

@@ -187,6 +187,10 @@ jobs:
     # seed-apt-cache / cache-esp-idf).
     if: github.event_name == 'push'
     timeout-minutes: 15
+    env:
+      # The composite action and the install below agree on this path by
+      # construction, not by matching the Python-side default
+      ESPHOME_ARDUINO8266_PREFIX: ~/.esphome-arduino8266
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -195,23 +199,9 @@ jobs:
         with:
           python-version: ${{ env.DEFAULT_PYTHON }}
           cache-key: ${{ needs.common.outputs.cache-key }}
-      - name: Resolve the native toolchain cache key
-        id: esp8266-native-cache-key
-        run: |
-          . venv/bin/activate
-          # Assignment form so errexit catches a resolver failure; a nested
-          # $(...) inside echo would silently yield a degenerate key
-          key=$(python -c 'from esphome.components.esp8266 import RECOMMENDED_ARDUINO_FRAMEWORK_VERSION as f; from esphome.arduino8266.framework import TOOLCHAIN_VERSION as t; print(f"{f}-{t}")')
-          [ -n "$key" ] || exit 1
-          echo "key=esp8266-native-$key" >> $GITHUB_OUTPUT
       - name: Cache the native toolchain
-        id: esp8266-native-cache
-        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
-        with:
-          path: ~/.cache/esphome/arduino8266
-          key: ${{ steps.esp8266-native-cache-key.outputs.key }}
+        uses: ./.github/actions/cache-arduino8266
       - name: Install the native toolchain
-        if: steps.esp8266-native-cache.outputs.cache-hit != 'true'
         run: |
           . venv/bin/activate
           python -c "from esphome.arduino8266.framework import check_and_install; from esphome.components.esp8266 import RECOMMENDED_ARDUINO_FRAMEWORK_VERSION; check_and_install(RECOMMENDED_ARDUINO_FRAMEWORK_VERSION)"
@@ -1181,6 +1171,7 @@ jobs:
       # Single source of truth -- the full list lives in
       # script/determine-jobs.py::ESP8266_NATIVE_TEST_COMPONENTS.
       TEST_COMPONENTS: ${{ needs.determine-jobs.outputs.esp8266-native-components }}
+      ESPHOME_ARDUINO8266_PREFIX: ~/.esphome-arduino8266
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -1191,27 +1182,8 @@ jobs:
           python-version: ${{ env.DEFAULT_PYTHON }}
           cache-key: ${{ needs.common.outputs.cache-key }}
 
-      # ~110 MB of framework + toolchain (no ccache: the seed job saves
-      # before any compile runs, so the store would always be empty). The versions
-      # are pinned in code, not in a hashable file, so resolve them for the
-      # key (actions/cache never overwrites a key, so a bump must change it).
-      # PRs are restore-only; the shared entry is seeded on pushes to dev by
-      # seed-esp8266-native-cache, mirroring the seed-apt-cache scoping.
-      - name: Resolve the native toolchain cache key
-        id: esp8266-native-cache-key
-        run: |
-          . venv/bin/activate
-          # Assignment form so errexit catches a resolver failure; a nested
-          # $(...) inside echo would silently yield a degenerate key
-          key=$(python -c 'from esphome.components.esp8266 import RECOMMENDED_ARDUINO_FRAMEWORK_VERSION as f; from esphome.arduino8266.framework import TOOLCHAIN_VERSION as t; print(f"{f}-{t}")')
-          [ -n "$key" ] || exit 1
-          echo "key=esp8266-native-$key" >> $GITHUB_OUTPUT
-
-      - name: Restore the native toolchain
-        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
-        with:
-          path: ~/.cache/esphome/arduino8266
-          key: ${{ steps.esp8266-native-cache-key.outputs.key }}
+      - name: Cache the native toolchain
+        uses: ./.github/actions/cache-arduino8266
 
       - name: Run native toolchain compile test
         run: |