feat: QEMU headless boot test in CI, updated skills + references

CI now runs a headless QEMU boot test after the smoke test:
- Boots ISO with -nographic, captures serial output
- Watches for "Press Enter to start installation" (pass)
- Detects kernel panic or initramfs shell (fail)
- 120 second timeout, runs as continue-on-error

Also: updated iso-debug reference with embedded vs appended EFI
findings from real hardware testing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-iso-dev.yml

@@ -109,6 +109,18 @@ jobs:
           fi
           echo "SMOKE TEST PASSED"
 
+      - name: QEMU boot test
+        timeout-minutes: 5
+        continue-on-error: true
+        run: |
+          ISO=$(ls image-recipe/results/archipelago-installer-unbundled-*.iso 2>/dev/null | head -1)
+          if [ -n "$ISO" ] && command -v qemu-system-x86_64 >/dev/null 2>&1; then
+            echo "Running headless QEMU boot test..."
+            bash image-recipe/test-iso-headless.sh "$ISO" 120
+          else
+            echo "Skipping QEMU test (no ISO or QEMU not available)"
+          fi
+
       - name: Copy to Builds
         run: |
           ISO=$(ls image-recipe/results/archipelago-installer-unbundled-*.iso 2>/dev/null | head -1)