Fix: quote ${CLAUDE_PLUGIN_ROOT} so hooks work on paths with spaces

Both SessionStart and UserPromptSubmit hook commands passed
${CLAUDE_PLUGIN_ROOT} unquoted, so the shell split the expansion
on whitespace whenever a user's plugin root contained a space
(e.g. /Users/Tyler Laprade/...). Node received a truncated path
and errored with "Cannot find module '/Users/Tyler'", preventing
the plugin from loading.

Wrapping the variable in double quotes keeps the path intact on
any POSIX-style shell and has no effect on paths without spaces.

Fixes #157

.claude-plugin/plugin.json

@@ -11,7 +11,7 @@
         "hooks": [
           {
             "type": "command",
-            "command": "node ${CLAUDE_PLUGIN_ROOT}/hooks/caveman-activate.js",
+            "command": "node \"${CLAUDE_PLUGIN_ROOT}/hooks/caveman-activate.js\"",
             "timeout": 5,
             "statusMessage": "Loading caveman mode..."
           }
@@ -23,7 +23,7 @@
         "hooks": [
           {
             "type": "command",
-            "command": "node ${CLAUDE_PLUGIN_ROOT}/hooks/caveman-mode-tracker.js",
+            "command": "node \"${CLAUDE_PLUGIN_ROOT}/hooks/caveman-mode-tracker.js\"",
             "timeout": 5,
             "statusMessage": "Tracking caveman mode..."
           }