test: deflake windows graph script tests

python3 first-start on fresh Windows runners (AV interpreter scans) blew
the 5s/10s/30s script timeouts. Drop the incidental python3 spawns from
the bash fixtures (pure-bash JSON extraction) and give the genuinely
python tests 60s headroom.

src/graph/executor.rs

@@ -695,6 +695,7 @@ nodes:
     type: script
     script: doubler.py
     state_updates: {}
+    timeout: 60
   done:
     type: end
     output: "{{doubled}}"