fix(ci): document platform tag format in sync workflow dispatch input

Platform release-please tags are prefixed: azurelocal-platform-v<ver>,
not bare v<ver>. Clarify the workflow_dispatch input description so future
manual runs don't pass an invalid ref.

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

Author: Kristopher Turner

.github/workflows/sync-standards.yml

@@ -13,7 +13,7 @@ on:
   workflow_dispatch:
     inputs:
       platform_ref:
-        description: "Platform ref to sync from (branch or tag)"
+        description: "Platform ref to sync from (branch or full tag, e.g. main or azurelocal-platform-v0.1.0)"
         required: false
         default: "main"
   repository_dispatch: