fix: stabilize /gsd-progress flag routing parse contract (#3420)

* fix: stabilize /gsd-progress flag parsing prompt contract (#3418)

* chore: set changeset PR reference to #3420

commands/gsd/progress.md

@@ -35,7 +35,8 @@ Three modes:
 </execution_context>
 
 <process>
-Parse the first token of $ARGUMENTS:
+Arguments provided: "$ARGUMENTS"
+Parse the first token from the provided arguments:
 - If it is `--next`: strip the flag, execute the next workflow (passing remaining args e.g. --force).
 - If it is `--do`: strip the flag, pass remainder as freeform intent to the do workflow.
 - Otherwise: execute the progress workflow end-to-end (pass --forensic through if present).