fix(scenarios): validate instance_count range and guard against negative values

Per qodo-code-review bot on PR krkn-chaos#1219:
- Add instance_count type and range validation in BaseNetworkChaosConfig.validate()
  so negative or non-int values from YAML are caught early with a clear error
- Tighten sampling guard to require isinstance(int) and instance_count > 0
  before calling random.sample(), preventing a runtime crash on negative values

Signed-off-by: NETIZEN-11 <niteshkumar121411@gmail.com>

Author: NETIZEN-11

krkn/scenario_plugins/network_chaos_ng/models.py

@@ -43,6 +43,10 @@ def validate(self) -> list[str]:
             errors.append("wait_duration must be an int")
         if not isinstance(self.test_duration, int):
             errors.append("test_duration must be an int")
+        if not isinstance(self.instance_count, int):
+            errors.append("instance_count must be an int")
+        elif self.instance_count < 0:
+            errors.append("instance_count must be >= 0")
         return errors
 
 

krkn/scenario_plugins/network_chaos_ng/network_chaos_ng_scenario_plugin.py

@@ -68,7 +68,8 @@ def run(
                         )
 
                     if (
-                        network_chaos_config.instance_count != 0
+                        isinstance(network_chaos_config.instance_count, int)
+                        and network_chaos_config.instance_count > 0
                         and len(targets) > network_chaos_config.instance_count
                     ):
                         targets = random.sample(