docs: update README for v1.20.0

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -505,7 +505,8 @@ You're never locked in. The system adapts.
 | `/gsd:add-todo [desc]` | Capture idea for later |
 | `/gsd:check-todos` | List pending todos |
 | `/gsd:debug [desc]` | Systematic debugging with persistent state |
-| `/gsd:quick` | Execute ad-hoc task with GSD guarantees |
+| `/gsd:quick [--full]` | Execute ad-hoc task with GSD guarantees (`--full` adds plan-checking and verification) |
+| `/gsd:health [--repair]` | Validate `.planning/` directory integrity, auto-repair with `--repair` |
 
 <sup>¹ Contributed by reddit user OracleGreyBeard</sup>