fix(#2697): replace retired /gsd: prefix with /gsd- in all user-facing text (#2699)

All workflow, command, reference, template, and tool-output files that
surfaced /gsd:<cmd> as a user-typed slash command have been updated to
use /gsd-<cmd>, matching the Claude Code skill directory name.

Closes #2697

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

get-shit-done/workflows/pause-work.md

@@ -1,5 +1,5 @@
 <purpose>
-Create structured `.planning/HANDOFF.json` and `.continue-here.md` handoff files to preserve complete work state across sessions. The JSON provides machine-readable state for `/gsd:resume-work`; the markdown provides human-readable context.
+Create structured `.planning/HANDOFF.json` and `.continue-here.md` handoff files to preserve complete work state across sessions. The JSON provides machine-readable state for `/gsd-resume-work`; the markdown provides human-readable context.
 </purpose>
 
 <required_reading>
@@ -226,7 +226,7 @@ Current state:
 - Blockers: [count] ({human_actions_pending count} need human action)
 - Committed as WIP
 
-To resume: /gsd:resume-work
+To resume: /gsd-resume-work
 
 ```
 </step>