Security: Remove contents:write from hypatia-dispatch-intake

The workflow is triggered by repository_dispatch events which can
come from external sources. Having contents:write permission allowed
arbitrary writes to the findings-submissions branch without PR review.

Changed to contents:read - the workflow will now fail safely when
attempting to push, preventing unauthorized external writes.

Fixes: Risk of breach via external dispatch triggers

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

Author: hyperpolymath

.github/workflows/hypatia-dispatch-intake.yml

@@ -11,7 +11,7 @@ on:
       - hypatia-general-findings
 
 permissions:
-  contents: write
+  contents: read
 
 jobs:
   intake: