fix: agent-smoke get_fns — use literal [ \t] for busybox awk compat

Busybox awk in Alpine CI has incomplete POSIX character class support;
[[:space:]] intermittently fails to match, causing function definitions
to be missed from LIB_FUNS. Replace with literal [ \t] patterns.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.woodpecker/agent-smoke.sh

@@ -21,9 +21,9 @@ FAILED=0
 # Uses awk instead of grep -Eo for busybox/Alpine compatibility (#296).
 get_fns() {
   local f="$1"
-  awk '/^[[:space:]]*[a-zA-Z_][a-zA-Z0-9_]+[[:space:]]*\(\)/ {
-    sub(/^[[:space:]]+/, "")
-    sub(/[[:space:]]*\(\).*/, "")
+  awk '/^[ \t]*[a-zA-Z_][a-zA-Z0-9_]+[ \t]*\(\)/ {
+    sub(/^[ \t]+/, "")
+    sub(/[ \t]*\(\).*/, "")
     print
   }' "$f" 2>/dev/null | sort -u || true
 }