Fix client_payload serialization in gh api dispatch call

Use jq + --input to pass client_payload as a JSON object.
The -F flag was serializing it as a string, causing a 422 from GitHub.

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

Author: m-messer

.github/workflows/release.yml

@@ -73,7 +73,7 @@ jobs:
         env:
           GH_TOKEN: ${{ secrets.SHIMMY_DEPLOY_TOKEN }}
         run: |
+          jq -n --arg v "${{ steps.version.outputs.version }}" \
+            '{"event_type":"release","client_payload":{"shimmy_version":$v}}' | \
           gh api repos/${{ github.repository_owner }}/evaluation-function-base/dispatches \
-            --method POST \
-            -f event_type=release \
-            -F client_payload='{"shimmy_version": "${{ steps.version.outputs.version }}"}'
+            --method POST --input -