feat(hooks): add --hook-output flag reporting removed comments

Emits Claude Code PostToolUse JSON so automated comment removal is
announced in-context instead of appearing as a silent mutation.
--install-hook now writes 'shush --changes-only --hook-output'.

Bump version to 0.6.0.

internal/hooks/hooks.go

@@ -125,7 +125,7 @@ func SaveSettings(path string, settings *ClaudeSettings) error {
 func CreateShushHookEntry() HookEntry {
 	return HookEntry{
 		Type:    "command",
-		Command: "shush --changes-only",
+		Command: "shush --changes-only --hook-output",
 		Timeout: 5,
 	}
 }
@@ -208,7 +208,7 @@ func AddShushHook(settings *ClaudeSettings) error {
 
 	shushHook := map[string]interface{}{
 		"type":    "command",
-		"command": "shush --changes-only",
+		"command": "shush --changes-only --hook-output",
 		"timeout": 5,
 	}