Fix install-breaking and live-boot bugs, verified on real hardware

Boot-critical (each confirmed with a real boot/install cycle, not just
code review):

- Live ISO's liveuser shell is zsh, but Hyprland autostart was written
  to .bash_profile (never runs) — moved to .zprofile, and switched to
  start-hyprland (Hyprland's own watchdog wrapper; raw `exec Hyprland`
  is no longer the recommended launch method).
- copytoram (self-enables on most real hardware: non-optical boot +
  image < 4GiB + enough free RAM) unmounts /run/archiso/bootmnt, which
  unpackfs.conf and bos-copy-kernel both hardcoded as their source —
  broke the installer outright on real hardware, confirmed by forcing
  copytoram=y. Added a resolver step for unpackfs, and switched the
  kernel copy to /usr/lib/modules/$(uname -r)/vmlinuz (part of the live
  squashfs itself, unaffected by copytoram).
- BIOS installs got no bootloader — post-install.sh only ever ran the
  UEFI grub-install path despite BOS shipping bios.syslinux. Added a
  BIOS branch with disk auto-detection.
- @snapshots/@log/@cache were never real: iso/partition.conf's
  btrfsSubvolumes key isn't part of this Calamares version's partition
  module schema at all (same class of bug as the userShell fix below —
  silently ignored). Calamares only natively creates @ and @home.
  post-install.sh now creates the three subvolumes by hand after
  unpackfs, migrates existing /var/log + /var/cache content into them
  before mounting over, and adds the fstab entries — verified end to
  end on real hardware, including grub-btrfs generating bootable
  snapshot menu entries. The unmount step in the existing snapper
  create-config dance also gained retry + lazy-unmount fallback after
  a real chroot run hit a transient busy-mount race.
- Default shell was bash instead of zsh post-install: users.conf's
  top-level `userShell` key isn't part of this Calamares version's
  users module schema either — the real key is nested (user.shell).
- graphical-session.target ships RefuseManualStart=yes (systemd
  convention), so the earlier attempt to activate it from hyprland.lua
  silently failed and breadclipd (WantedBy=graphical-session.target)
  never started. Starts breadclipd.service directly instead.
- /etc/os-release was never set (showed "Arch Linux"); live boot never
  had quiet/splash/plymouth wired in (raw kernel scroll the whole
  time) despite BOS already shipping a complete bread-logo+spinner
  plymouth theme for the installed system.

Also: generalized build-local.sh's per-service skel baking (previously
only breadd.service was hand-committed; breadbox-sync/breadmill/
breadclipd never shipped), added the four new bakery packages to
BREAD_BINS, removed the redundant cliphist/fzf clipboard pipeline in
favor of breadclip, mirrored fastfetch's bread-logo config into skel,
and fixed a stale bos-update comment.

iso/airootfs/usr/local/bin/bos-copy-kernel

@@ -7,19 +7,40 @@
 # (the stock linux.preset points ALL_kver at /boot/vmlinuz-linux) and before the
 # `bootloader` module runs grub — otherwise the installed system is unbootable.
 #
-# Runs in the LIVE environment (Calamares shellprocess, dontChroot) so it can
-# read /run/archiso/bootmnt; the target root mount point is passed as $1.
+# Runs in the LIVE environment (Calamares shellprocess, dontChroot); the
+# target root mount point is passed as $1.
+#
+# The kernel is read from /usr/lib/modules/$(uname -r)/vmlinuz — part of the
+# live squashfs itself (the linux package always installs it there), not from
+# the ISO's separate arch/boot/x86_64/ dir under /run/archiso/bootmnt. That
+# mount gets torn down by archiso's own copytoram handling, which self-enables
+# on most real hardware, so depending on it here would leave $ROOT/boot empty
+# and the install unbootable on exactly the machines this is meant to run on.
 set -uo pipefail
 
 ROOT="${1:?target root required}"
-SRC="/run/archiso/bootmnt/arch/boot/x86_64"
+KVER="$(uname -r)"
+SRC_KERNEL="/usr/lib/modules/${KVER}/vmlinuz"
+SRC_BOOT="/run/archiso/bootmnt/arch/boot/x86_64"
 
 install -d -m 0755 "$ROOT/boot"
-cp -f "$SRC/vmlinuz-linux" "$ROOT/boot/vmlinuz-linux"
 
-# Microcode, if the live medium carries it (grub-mkconfig picks it up).
+if [ -f "$SRC_KERNEL" ]; then
+    cp -f "$SRC_KERNEL" "$ROOT/boot/vmlinuz-linux"
+elif [ -f "$SRC_BOOT/vmlinuz-linux" ]; then
+    echo "WARN: $SRC_KERNEL missing, falling back to $SRC_BOOT"
+    cp -f "$SRC_BOOT/vmlinuz-linux" "$ROOT/boot/vmlinuz-linux"
+else
+    echo "ERROR: no kernel image found (checked $SRC_KERNEL and $SRC_BOOT/vmlinuz-linux) — install would be unbootable" >&2
+    exit 1
+fi
+
+# Microcode, if the live medium carries it (grub-mkconfig picks it up). This
+# is best-effort: post-install.sh's mkinitcpio `microcode` HOOKS entry embeds
+# microcode from /usr/lib/firmware directly, so a missing standalone ucode.img
+# here is not boot-critical, unlike the kernel image above.
 for u in amd-ucode.img intel-ucode.img; do
-    [ -f "$SRC/$u" ] && cp -f "$SRC/$u" "$ROOT/boot/$u"
+    [ -f "$SRC_BOOT/$u" ] && cp -f "$SRC_BOOT/$u" "$ROOT/boot/$u"
 done
 
 # Replace the archiso initramfs setup that unpackfs copied from the live medium.