fix(guard): add pre-emptive write operation entries for set_variable, upload_release_asset, sync_fork

Agent-Logs-Url: https://github.com/github/gh-aw-mcpg/sessions/8c76a5cb-3e66-4cce-a600-147883fad9c3

Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

Author: Copilot

guards/github-guard/rust-guard/src/tools.rs

@@ -43,6 +43,9 @@ pub const WRITE_OPERATIONS: &[&str] = &[
     "enable_workflow",    // gh workflow enable
     "disable_workflow",   // gh workflow disable
     "set_secret",         // gh secret set
+    "set_variable",         // gh variable set
+    "upload_release_asset", // gh release upload
+    "sync_fork",            // gh repo sync
 ];
 
 /// Read-write operations that both read and modify data