fix(arm64): tr -d '[:space:]' is parsed as literal char-set by busybox 1.30.1

Ubuntu's busybox-static 1.30.1 (which we use for the ARM64 rootfs after
piCore64's BusyBox crashes in QEMU virt) doesn't recognize POSIX character
classes. `tr -d '[:space:]'` is interpreted as "delete any of the literal
characters [, :, s, p, a, c, e, ]" — so every s/p/a/c/e in module names and
sysctl keys gets eaten.

Symptoms in the boot log:
  virtio_net  -> virtio_nt   (e dropped)
  overlay     -> ovrly       (e, a dropped)
  bridge      -> bridg       (e dropped)
  nf_conntrack -> nf_onntrk  (c, a, c dropped)
  net.bridge.bridge-nf-call-iptables -> nt.bridg.bridg-nf-ll-itbl

Fix: use explicit whitespace chars `tr -d ' \t\r\n'` in both
30-kernel-modules.sh and 40-sysctl.sh. Works under any tr implementation.

Also: filter functions.sh out of the init.d stage-copy loop. It's a shared
library (sourced by init.sh), not a numbered stage. With it in init.d the
main loop runs it as a stage after stage 90, then panics with "Init
completed without exec'ing KubeSolo".

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

build/scripts/inject-kubesolo.sh

@@ -84,10 +84,15 @@ if [ "$INJECT_ARCH" = "arm64" ] && [ -x /bin/busybox ]; then
     fi
 fi
 
-# Init stages
+# Init stages — copy NN-name.sh files only. functions.sh is a shared library
+# (sourced by init.sh proper), not a numbered stage; if it ends up in init.d
+# the main loop will try to run it as a stage and fail.
 mkdir -p "$ROOTFS/usr/lib/kubesolo-os/init.d"
 for stage in "$PROJECT_ROOT"/init/lib/*.sh; do
     [ -f "$stage" ] || continue
+    case "$(basename "$stage")" in
+        functions.sh) continue ;;
+    esac
     cp "$stage" "$ROOTFS/usr/lib/kubesolo-os/init.d/"
     chmod +x "$ROOTFS/usr/lib/kubesolo-os/init.d/$(basename "$stage")"
 done