CP-43412: Clarify version input in Manual Prepare Release workflow

The "Version to release" workflow_dispatch input now shows an example
(1.2.3), making it clear the version must be entered without a "v" prefix.
The workflow prepends "v" itself when tagging, so a "v"-prefixed input
would produce a "vv1.2.3" tag and break the release-notes file lookup.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: evan-cz

.github/workflows/release-to-main.yml

@@ -4,7 +4,7 @@ on:
   workflow_dispatch:
     inputs:
       version:
-        description: "Version to release."
+        description: 'Version to release (e.g., "1.2.3").'
         required: true
 
 jobs: