Fix mcp-diff workflow triggers

Add push triggers to run on:
- Pushes to main branch (catches merges)
- Tag pushes (v*) for release comparisons against previous tags

The pull_request trigger alone doesn't run when commits are pushed
to PR branches via merge or direct push. Adding push triggers ensures
the diff runs in all expected scenarios.

Author: SamMorrowDrums

.github/workflows/mcp-diff.yml

@@ -2,6 +2,9 @@ name: MCP Server Diff
 
 on:
   pull_request:
+  push:
+    branches: [main]
+    tags: ['v*']
 
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