build: scope ABI-staleness invalidation to the config being built

The relibc-consumer ABI sweep looped over the whole shared repo/*.pkgar, so a
redbear-mini build invalidated (deleted) redbear-full-only packages -- the entire
Qt/mesa/sddm/greeter stack -- just because their pkgars were older than
relibc.pkgar. Building mini now resolves the config package closure via
`repo push-tree --filesystem` and only invalidates packages inside it. Build
mini, touch mini; full artifacts are never collateral. No env flag needed for
the common case.

local/scripts/build-redbear.sh

@@ -739,8 +739,36 @@ if [ "$NO_CACHE" != "1" ]; then
             *) return 1 ;;
         esac
     }
+    # ── Config-scoped ABI invalidation ──────────────────────────────────
+    # repo/ is shared across configs, so a `redbear-mini` build must NOT nuke
+    # packages that only `redbear-full` builds (Qt, mesa, sddm, ...) just because
+    # their pkgars sit in the repo older than relibc.pkgar. Resolve the closure
+    # of the config being built and only ever invalidate packages inside it.
+    # No env flag needed — you named the config, so we know it's mini not full.
+    declare -A _config_pkg_set
+    _config_scoped=0
+    _cfg_file="$PROJECT_ROOT/config/$CONFIG.toml"
+    if [ -f "$_cfg_file" ]; then
+        while read -r _p; do
+            [ -n "$_p" ] && _config_pkg_set["$_p"]=1
+        done < <(timeout 120 "$PROJECT_ROOT/target/release/repo" push-tree \
+                     --filesystem="$_cfg_file" 2>/dev/null \
+                   | sed -E 's/^[^A-Za-z0-9_]+//' | awk '{print $1}' | grep -E '^[A-Za-z0-9]')
+        [ "${#_config_pkg_set[@]}" -gt 0 ] && _config_scoped=1
+    fi
+    if [ "$_config_scoped" = "1" ]; then
+        echo ">>> ABI-staleness scoped to $CONFIG (${#_config_pkg_set[@]} pkgs); other configs' repo packages untouched."
+    else
+        echo ">>> NOTE: could not resolve $CONFIG package closure; ABI sweep is repo-wide (fallback)."
+    fi
+    _pkg_in_config() {
+        # true unless we have a config closure and pkg is outside it
+        [ "$_config_scoped" != "1" ] && return 0
+        [ -n "${_config_pkg_set[$1]:-}" ]
+    }
     invalidate_consumer() {
         local pkg="$1"
+        _pkg_in_config "$pkg" || return 0
         rm -f "$REPO_DIR/$pkg".*
         find "$PROJECT_ROOT/recipes" "$PROJECT_ROOT/local/recipes" \
             -path "*/$pkg/target" -type d -exec rm -rf {} + 2>/dev/null || true
@@ -762,6 +790,7 @@ if [ "$NO_CACHE" != "1" ]; then
         for _pkgar in "$REPO_DIR"/*.pkgar; do
             [ -f "$_pkgar" ] || continue
             _pkg="$(basename "$_pkgar" .pkgar)"
+            _pkg_in_config "$_pkg" || continue
             if _rb_preserve_toolchain "$_pkg"; then
                 echo ">>> preserving ABI-inert toolchain pkg '$_pkg' (consumer relinks;" \
                      "set REDBEAR_FORCE_TOOLCHAIN_RECOOK=1 to force a full re-cook)."
@@ -775,6 +804,7 @@ if [ "$NO_CACHE" != "1" ]; then
             [ -f "$_pkgar" ] || continue
             _pkg="$(basename "$_pkgar" .pkgar)"
             [ "$_pkg" = "relibc" ] && continue
+            _pkg_in_config "$_pkg" || continue
             _rb_preserve_toolchain "$_pkg" && continue
             _pkg_ts=$(stat -c %Y "$_pkgar" 2>/dev/null || echo "0")
             if [ "$relibc_ts" != "0" ] && [ "$relibc_ts" -gt "$_pkg_ts" ]; then