test(kugetsu-helpers): add unit test suite and fix None/null handling

- Add test suite at skills/kugetsu-helpers/tests/test-kugetsu-helpers.sh
- 11 unit tests covering check-status, delegate-to-pm, get-pm-session, etc.
- Fix bug: Python print(None) outputs literal "None" string, not empty
- All tests pass

skills/kugetsu-helpers/scripts/kugetsu-helpers

@@ -29,7 +29,7 @@ kugetsu_check_status() {
     fi
     
     PM_AGENT=$(kugetsu_get_pm_session)
-    if [ -z "$PM_AGENT" ] || [ "$PM_AGENT" = "null" ]; then
+    if [ -z "$PM_AGENT" ] || [ "$PM_AGENT" = "null" ] || [ "$PM_AGENT" = "None" ]; then
         echo "pm_agent_missing"
         return
     fi
@@ -46,7 +46,7 @@ kugetsu_delegate_to_pm() {
     fi
     
     local pm_session=$(kugetsu_get_pm_session)
-    if [ -z "$pm_session" ] || [ "$pm_session" = "null" ]; then
+    if [ -z "$pm_session" ] || [ "$pm_session" = "null" ] || [ "$pm_session" = "None" ]; then
         echo "Error: PM agent session not found. Run 'kugetsu init' first."
         return 1
     fi
@@ -99,7 +99,7 @@ kugetsu_continue_dev_session() {
 
 kugetsu_fix_pm_permissions() {
     local pm_session=$(kugetsu_get_pm_session)
-    if [ -z "$pm_session" ] || [ "$pm_session" = "null" ]; then
+    if [ -z "$pm_session" ] || [ "$pm_session" = "null" ] || [ "$pm_session" = "None" ]; then
         echo "Error: PM agent session not found"
         return 1
     fi