fix(ci): cache data/examples.json with examples/ + correct hash key

Two related bugs found in the first matrix-parallel run:

1. `make components` (build/make.py) writes to data/examples.json, not
   into examples/. My cache path was only `examples`, so on cache hit
   data/examples.json was missing — Hugo failed in the jupyter-example
   shortcode with:

     ERROR jupyter-example: Example 'landing' not found for language
       'Python' in examples.json. Run 'python3 build/local_examples.py'
       to generate data.

2. Cache key used data/components_local/index.json, but `make components`
   (without --stack flag) reads the default data/components/index.json.
   Wrong file would have meant the cache never invalidated when the
   component stack changed.

Fix: include both paths in cache and key off the correct stack file:

  path: |
    examples
    data/examples.json
  key: components-${{ runner.os }}-${{ hashFiles('Makefile', 'build/**', 'data/components/index.json') }}

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: EliShteinman

.github/workflows/airgap-build.yml

@@ -248,12 +248,14 @@ jobs:
           python3 -m venv ./venv
           ./venv/bin/pip install --quiet -r requirements.txt
 
-      - name: Restore examples
+      - name: Restore examples + data/examples.json
         id: cache-examples
         uses: actions/cache@v4
         with:
-          path: examples
-          key: components-${{ runner.os }}-${{ hashFiles('Makefile', 'build/**', 'data/components_local/index.json') }}
+          path: |
+            examples
+            data/examples.json
+          key: components-${{ runner.os }}-${{ hashFiles('Makefile', 'build/**', 'data/components/index.json') }}
 
       - name: make components (cache miss)
         if: steps.cache-examples.outputs.cache-hit != 'true'
@@ -410,12 +412,14 @@ jobs:
           python3 -m venv ./venv
           ./venv/bin/pip install --quiet -r requirements.txt
 
-      - name: Restore examples
+      - name: Restore examples + data/examples.json
         id: cache-examples
         uses: actions/cache@v4
         with:
-          path: examples
-          key: components-${{ runner.os }}-${{ hashFiles('Makefile', 'build/**', 'data/components_local/index.json') }}
+          path: |
+            examples
+            data/examples.json
+          key: components-${{ runner.os }}-${{ hashFiles('Makefile', 'build/**', 'data/components/index.json') }}
 
       - name: make components (cache miss)
         if: steps.cache-examples.outputs.cache-hit != 'true'