Release v3.6.2: Fix Linux compatibility in polyglot hook wrapper

Fixed POSIX compatibility issue in hooks/run-hook.cmd that caused
"Bad substitution" errors on Ubuntu/Debian systems where /bin/sh is dash.

Changes:
- Replaced bash-specific ${BASH_SOURCE[0]:-$0} with POSIX-compliant $0
- Tested with both bash and sh (POSIX mode) on macOS
- Updated version to 3.6.2 in all required files

Fixes #141

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "superpowers",
   "description": "Core skills library for Claude Code: TDD, debugging, collaboration patterns, and proven techniques",
-  "version": "3.6.1",
+  "version": "3.6.2",
   "author": {
     "name": "Jesse Vincent",
     "email": "jesse@fsck.com"