fix(claude): restore namespaced /gsd:<command> references (#3452)

* fix(claude): restore namespaced /gsd:<command> references

* test(claude): align slash-command expectations to /gsd: form

* test(claude): align generated command references to /gsd:

* test(claude): finish /gsd: namespace expectation updates

get-shit-done/workflows/execute-phase/steps/codebase-drift-gate.md

@@ -34,7 +34,7 @@ New migrations:
 New route modules:
   - {path}
 
-Run /gsd-map-codebase --paths {affected_paths} to refresh planning context.
+Run /gsd:map-codebase --paths {affected_paths} to refresh planning context.
 ```
 
 Then continue to `verify_phase_goal`. Do NOT block. Do NOT spawn anything.