Keep one extras list per device instead of per version

The package lists were stored as config_<version>/packages_<device>_<version>.txt,
but the version dimension was pure duplication: the Linksys MX8500 extras were
byte-identical across 24.10.4, 25.12.0, 25.12.2 and 25.12.4, and the Cudy lists
only ever changed with the device, never with the release.

Your packages now live in packages/<device-id>.txt, one file per device and
independent of the OpenWrt version. The built-in part is fetched per release
anyway, so upgrading needs no file changes at all.

The combined list is a build artefact and moves to .generated/, which is
gitignored, along with the buildinfo saved by --save-buildinfo --offline.

This removes work rather than adding it: because the generated file is now
entirely machine-owned, the sentinel comments, the in-section replacement state
machine and the "line containing base-files and libc is the old generated one"
migration heuristic are all gone. Hand-written content is isolated in the extras
file, generated content in .generated/.

Also fix version detection when a script is run from the helper directory. The
helper checkout is its own git repository inside the OpenWrt worktree, so git
commands there described the helper repo -- a checkout of OpenWrt 25.12.5 was
reported as SNAPSHOT because the helper repo is on main. Version queries are now
anchored to the OpenWrt tree.

The config_* archives are deleted; git history keeps them. That includes
config_24.10.4/apply-dahdi-patches.sh, which only applied to 24.10.4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

lib-openwrt-upstream.sh

@@ -71,6 +71,21 @@ require_python3() {
   fi
 }
 
+# The helper checkout is itself a git repository living inside the OpenWrt
+# worktree, so plain git commands run from here describe the HELPER repo.
+# Every version query must be anchored to the OpenWrt tree instead.
+find_openwrt_root() {
+  local d
+  for d in "$PWD" "$(dirname -- "${LIB_SCRIPT_DIR:-$PWD}")"; do
+    [ -n "$d" ] || continue
+    if [ -f "$d/feeds.conf.default" ] && [ -f "$d/Makefile" ] && [ -d "$d/scripts" ]; then
+      ( cd -- "$d" && pwd -P )
+      return 0
+    fi
+  done
+  return 1
+}
+
 require_openwrt_root() {
   if [ ! -f feeds.conf.default ] || [ ! -f Makefile ] || [ ! -d scripts ]; then
     err "Must run inside the OpenWrt root directory."
@@ -155,19 +170,24 @@ detect_version() {
     return 0
   fi
 
-  if ! git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
-    err "Not inside a Git repository and no --version given."
+  local root=""
+  if ! root="$(find_openwrt_root)"; then
+    err "Cannot locate the OpenWrt source tree; pass --version <ver> explicitly."
+    exit 1
+  fi
+  if ! git -C "$root" rev-parse --is-inside-work-tree >/dev/null 2>&1; then
+    err "'$root' is not a Git repository and no --version was given."
     exit 1
   fi
 
-  if tag="$(git describe --tags --exact-match HEAD 2>/dev/null)"; then
+  if tag="$(git -C "$root" describe --tags --exact-match HEAD 2>/dev/null)"; then
     ver="${tag#v}"
     info "HEAD is exactly at tag $tag; using version $ver."
     echo "$ver"
     return 0
   fi
 
-  if branch="$(git symbolic-ref --quiet --short HEAD 2>/dev/null)"; then
+  if branch="$(git -C "$root" symbolic-ref --quiet --short HEAD 2>/dev/null)"; then
     case "$branch" in
       main | master)
         info "On branch '$branch'; using SNAPSHOT."
@@ -177,10 +197,10 @@ detect_version() {
       openwrt-* | [0-9]*)
         local series="${branch#openwrt-}"
         # --merged HEAD keeps tags from unrelated branches out of the picture.
-        tag="$(git tag --merged HEAD -l "v${series}.*" 2>/dev/null |
+        tag="$(git -C "$root" tag --merged HEAD -l "v${series}.*" 2>/dev/null |
           grep -v -- '-rc' | sort -V | tail -n 1)"
         if [ -n "$tag" ]; then
-          drift="$(git rev-list --count "$tag..HEAD" 2>/dev/null || echo 0)"
+          drift="$(git -C "$root" rev-list --count "$tag..HEAD" 2>/dev/null || echo 0)"
           if [ "$drift" -gt 0 ]; then
             warn "HEAD is $drift commit(s) past $tag."
             warn "The downloaded config describes the release, not your tree."
@@ -194,9 +214,9 @@ detect_version() {
     esac
   fi
 
-  if tag="$(git describe --tags --long 2>/dev/null)"; then
+  if tag="$(git -C "$root" describe --tags --long 2>/dev/null)"; then
     tag="${tag%-*-g*}"
-    drift="$(git rev-list --count "$tag..HEAD" 2>/dev/null || echo 0)"
+    drift="$(git -C "$root" rev-list --count "$tag..HEAD" 2>/dev/null || echo 0)"
     warn "HEAD is not at a tag; nearest is $tag ($drift commit(s) behind HEAD)."
     if [ "$ASSUME_YES" != true ] &&
       ! confirm "Use version ${tag#v}?" no; then