fix(ci): correct cache key path for west manifest (#832)

hashFiles('manifest-dir/west.yml') never matched any file, so the cache
key was always identical regardless of ZMK version changes. This meant
upgrading the fork revision in config/west.yml would silently use stale
cached modules. Fix both Legacy and Clique job cache keys to point at
the actual manifest path.

Made-with: Cursor

Author: anyasabo

.github/workflows/build.yml

@@ -31,7 +31,7 @@ jobs:
             zephyr/
             bootloader/
             zmk/
-          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('manifest-dir/west.yml') }}
+          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('config/west.yml') }}
           restore-keys: |
             ${{ runner.os }}-build-${{ env.cache-name }}-
             ${{ runner.os }}-build-
@@ -87,7 +87,7 @@ jobs:
             zephyr/
             bootloader/
             zmk/
-          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('manifest-dir/west.yml') }}
+          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('config/west.yml') }}
           restore-keys: |
             ${{ runner.os }}-build-${{ env.cache-name }}-
             ${{ runner.os }}-build-