iso: fix packages.x86_64 (no inline comments; gstreamer-vaapi -> gst-plugin-va)

Inline comments after a package name broke kitty/flatpak (became invalid
names with trailing whitespace). gstreamer-vaapi was removed from Arch.
calamares is AUR-only -> commented pending a [tanin] rebuild decision.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

iso/build-profile/airootfs/usr/local/bin/choose-mirror

@@ -0,0 +1,29 @@
+#!/bin/bash
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+get_cmdline() {
+    local param
+    for param in $(</proc/cmdline); do
+        case "${param}" in
+            "${1}="*)
+                echo "${param##*=}"
+                return 0
+                ;;
+        esac
+    done
+}
+
+mirror="$(get_cmdline mirror)"
+[[ "$mirror" == 'auto' ]] && mirror="$(get_cmdline archiso_http_srv)"
+[[ -n "$mirror" ]] || exit 0
+
+mv /etc/pacman.d/mirrorlist /etc/pacman.d/mirrorlist.orig
+cat >/etc/pacman.d/mirrorlist <<EOF
+#
+# Arch Linux repository mirrorlist
+# Generated by archiso
+#
+
+Server = ${mirror%%/}/\$repo/os/\$arch
+EOF