Address review feedback on the Amiga packaging PR.

Keep Amiga-specific files under amiga/, cache the pinned LHa binary in
CI, and make it explicit that the workflow artifact is not an official
release.

Co-authored-by: Cursor <cursoragent@cursor.com>

.github/workflows/amiga.yml

@@ -1,5 +1,10 @@
 name: amiga
 
+# Verifies that AmigaOS 3/4 and MorphOS still cross-compile. The uploaded
+# json-c.lha is a CI convenience artifact only — official json-c releases
+# remain source-only. Aminet uploads are a separate, manual process and
+# are not published from this job.
+
 on: [push, pull_request, workflow_dispatch]
 
 concurrency:
@@ -14,11 +19,19 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 120
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
       # Ubuntu's `lha` package is lhasa: extract-only, cannot create archives.
       # Build LHa for UNIX (https://github.com/jca02266/lha) instead.
+      - name: Cache LHa for UNIX
+        id: cache-lha
+        uses: actions/cache@v6
+        with:
+          path: ~/.local/bin/lha
+          key: lha-16619b066b189ef289bb8b07b37d1c38d550da99-${{ runner.os }}
+
       - name: Install LHa for UNIX
+        if: steps.cache-lha.outputs.cache-hit != 'true'
         working-directory: ${{runner.temp}}
         run: |
           sudo apt-get update
@@ -31,7 +44,9 @@ jobs:
           ./configure --prefix="$HOME/.local"
           make -j"$(nproc)"
           make install
-          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+
+      - name: Add LHa to PATH
+        run: echo "$HOME/.local/bin" >> "$GITHUB_PATH"
 
       - name: Check lha can create archives
         run: |
@@ -49,9 +64,9 @@ jobs:
           wait
 
       - name: Build and package
-        run: ./package-amiga.sh
+        run: ./amiga/package-amiga.sh
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v7
         with:
           name: json-c.lha
           path: dist/json-c.lha