test: add stale /gsd: colon reference regression guard (#1753)

* test: add stale /gsd: colon reference regression guard

Fixes #1748

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

* fix: replace 39 stale /gsd: colon references with /gsd- hyphen format

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

tests/workspace.test.cjs

@@ -1,7 +1,7 @@
 /**
  * GSD Workspace Tests
  *
- * Tests for /gsd:new-workspace, /gsd:list-workspaces, /gsd:remove-workspace
+ * Tests for /gsd-new-workspace, /gsd-list-workspaces, /gsd-remove-workspace
  * init functions and integration with gsd-tools routing.
  */