fix: derive pack install guides from the registry

The pack README's one-line install was written per platform: ROCKNIX and MiSTer had none, EmuDeck's Windows edition was told to open Konsole, and RomM users were sent to library/bios/ whatever their firmware template. The automatic section now follows each platform's install.detect systems, the EmuDeck and RomM manual steps name every layout, and the download page lists EmuDeck under Windows and macOS.

scripts/generate_pack.py

@@ -1229,12 +1229,12 @@ def generate_pack(
           undecidable_slots=slot_undecidable,
           narrowings=narrowings,
           system_filter=system_filter,
-          bios_paths=[
-              str(detect.get("bios_path", ""))
-              for detect in (
-                  _pack_registry.get(platform_name, {}).get("install", {}) or {}
-              ).get("detect", [])
-          ],
+          detect=(
+              _pack_registry.get(platform_name, {}).get("install", {}) or {}
+          ).get("detect", []),
+          standalone_copies=(
+              _pack_registry.get(platform_name, {}).get("install", {}) or {}
+          ).get("standalone_copies", []),
       )
       _write_generated_member(zf, "README.txt", readme_text)