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/types/types.go

@@ -14,6 +14,7 @@ type CLI struct {
 	ContextLines  int              `short:"c" help:"Number of context lines to show in preview mode (default: from config)" default:"-1"`
 	LLM           bool             `help:"Show LLM-friendly usage guide"`
 	ChangesOnly   bool             `help:"Remove comments only from git changes (staged + unstaged + untracked)"`
+	HookOutput    bool             `help:"Emit Claude Code PostToolUse JSON reporting removed comments (for use in hooks)"`
 	Staged        bool             `help:"Remove comments only from staged git changes"`
 	Unstaged      bool             `help:"Remove comments only from unstaged git changes"`
 	InstallHook   bool             `help:"Install Claude Code hooks for automatic comment cleanup"`