fix(interactive): parse case alternatives in get_kernel_info_for_branch (#8957)

Fixes #8957.

The awk parser in get_kernel_info_for_branch() searched the family
conf for `^[[:space:]]*<branch>\)`, which matches a single-pattern
case label like `current)` but NOT a case label with alternation
like `vendor | vendor-rt)`. With no match, the function returned
an empty description and the menu fell back to a hardcoded label
("Vendor BSP kernel" for the vendor branch), so any custom
KERNEL_DESCRIPTION inside an alternation block was silently lost.

Fix: extract the label (everything before the closing paren),
split on `|` (with optional surrounding whitespace) and check each
alternative against the requested branch.

Real-world impact: families/k3.conf and families/k3-beagle.conf
both use `vendor | vendor-rt)` to share kernel/u-boot config
between the two branches. Their `KERNEL_DESCRIPTION` was effectively
dead code before this fix.

Single-label labels (`vendor-edge)`, `current)` etc.) continue to
match — they are just an n=1 case of the new alternation logic.

Assisted-by: Claude:claude-opus-4.7

Author: iav

lib/functions/configuration/interactive.sh

@@ -247,11 +247,21 @@ function get_kernel_info_for_branch() {
 	local search_branch="$1"
 	local conf_file="${SRC}/config/sources/families/${BOARDFAMILY}.conf"
 
+	# Recognises both `branch)` and `pat1 | pat2 | …)` case labels (#8957).
 	awk -v branch="$search_branch" '
     BEGIN { found=0; major_minor=""; desc="" }
-    /^[[:space:]]*[a-zA-Z0-9_-]+\)/ {
-        if ($0 ~ "^[[:space:]]*" branch "\\)") {
-            found=1
+    /^[[:space:]]*[a-zA-Z0-9_*?-][a-zA-Z0-9_*? |-]*\)/ {
+        label = $0
+        sub(/\).*/, "", label)
+        sub(/^[[:space:]]+/, "", label)
+        sub(/[[:space:]]+$/, "", label)
+        n = split(label, alts, /[[:space:]]*\|[[:space:]]*/)
+        matched = 0
+        for (i = 1; i <= n; i++) {
+            if (alts[i] == branch) { matched = 1; break }
+        }
+        if (matched) {
+            found = 1
             next
         } else if (found) {
             exit