amd gcn legacy support & kernel overhaul

- Fixed Mesa 32-bit dependency conflicts by removing mesa-va-drivers from gaming setup; mesa-libgallium now includes VA-API for Mesa >= 25.3.3, resolving solver errors with backports (Mesa 26.x).
- Removed corectrl detection and installation from AMD tools in gpu/amd_intel.sh (retained in System Tools checklist only).
- Added zutty terminal emulator option alongside alacritty for Debian 12+ in terminals.sh.
- Overhauled Kernel menu: replaced "Backports Kernel" with "Kernel" submenu offering Stable, RT, Cloud, and Backports options; removed hardcoded Debian 11 restriction (backports hidden only on Bullseye); headers now installed automatically with all kernel variants; NVIDIA warnings added for Backports (DKMS required) and RT (driver compatibility note).
- Implemented AMD GCN legacy driver migration: is_amd_legacy_gcn() function detects GCN 1.0/1.1 GPUs via whitelist of 85 PCI IDs; offers user prompt to force amdgpu module with GRUB parameters (radeon.si_support=0, radeon.cik_support=0, amdgpu.si_support=1, amdgpu.cik_support=1); safe sed-based injection into GRUB_CMDLINE_LINUX_DEFAULT with backup and idempotency check.
- Standardized UI across 27 checklist locations: unified text to "Check [*] the packages you want installed/updated on your system."; removed SCROLL_HINT variable entirely from all code; changed OK button to "Apply" in _checklist() and _inputbox() only (not in _msg/_menu).
- Reordered gaming menu checklists: i386 moved to top position, steam/mangohud positioned immediately after for better dependency flow.
- Enhanced kernel installation prompts: all variants (Stable, RT, Cloud, Backports) now display candidate version numbers in parentheses using apt-cache policy and madison queries.
- update readme

modules/gpu/_helpers.sh

@@ -112,6 +112,21 @@ is_nvidia_blackwell() {
     echo false
 }
 
+is_amd_legacy_gcn() {
+    local dev_id
+    dev_id=$(lspci -nn | grep -iE "VGA|3D" | grep -i amd | grep -oP '1002:\K[0-9a-fA-F]{4}' | head -n1)
+    [ -z "$dev_id" ] && { echo false; return; }
+
+    local legacy_ids
+    legacy_ids="6660|6664|6665|6667|6780|6784|6788|678a|6798|679a|679e|679f|3000|3001|6808|6809|6810|6811|6816|6817|6818|6819|6828|6829|682b|682c|6835|6837|683d|683f|6608|6609|6610|6611|6613|6617|1dcf|983d|6646|6649|664d|6650|6651|6658|665c|665d|67a0|67a1|67a2|67a8|67a9|67aa|67b0|67b1|67b8|67be|9830|9831|9832|9833|9834|9835|9836|9837|9838|9839|1304|1305|1306|1307|1309|130a|130b|130c|130d|130e|130f|1310|1311|1312|1313|1315|1316|1317|1318|131b|131c|131d|9850|9851|9852|9853|9854|9855|9856|9857|9858|9859|985a|985b|985c|985d|985e|985f"
+
+    if echo "$dev_id" | grep -qiE "^(${legacy_ids})$"; then
+        echo true
+    else
+        echo false
+    fi
+}
+
 _install_mesa_backports() {
     if [ "$(is_backports_enabled)" != "true" ]; then
         install_mesa_stable