refactor: Apply cache fixes directly to existing runner configs

- Update all runner configuration files with cache networking fixes:
  - config_docker.yaml
  - config_heavy.yaml
  - config_light.yaml
  - config_security.yaml
- Remove separate config_cache_fixed.yaml file
- Update troubleshooting scripts to use updated configs
- Update documentation to reference existing config files

All runner configs now have:
- Fixed cache host: host.docker.internal
- Fixed cache port: 44029
- Host networking for better container connectivity

This provides a cleaner approach by updating existing configs
instead of maintaining a separate fixed configuration file.

runners/config_docker.yaml

@@ -54,22 +54,20 @@ cache:
   # If it's empty, the cache data will be stored in $HOME/.cache/actcache.
   dir: ""
   # The host of the cache server.
-  # It's not for the address to listen, but the address to connect from job containers.
-  # So 0.0.0.0 is a bad choice, leave it empty to detect automatically.
-  host: ""
-  # The port of the cache server.
-  # 0 means to use a random available port.
-  port: 0
+  # Use host.docker.internal to allow containers to access the host
+  # This fixes the common networking issue where containers can't reach the cache server
+  host: "host.docker.internal"
+  # Use a fixed port instead of random to avoid connection issues
+  port: 44029
   # The external cache server URL. Valid only when enable is true.
   # If it's specified, act_runner will use this URL as the ACTIONS_CACHE_URL rather than start a server by itself.
   # The URL should generally end with "/".
   external_server: ""
 
 container:
-  # Specifies the network to which the container will connect.
-  # Could be host, bridge or the name of a custom network.
-  # If it's empty, act_runner will create a network automatically.
-  network: ""
+  # Use host network to avoid Docker networking issues with cache
+  # This ensures containers can access the cache server on the host
+  network: "host"
   # Whether to use privileged mode or not when launching task containers (privileged mode is required for Docker-in-Docker).
   privileged: false
   # And other options to be used when the container is started (eg, --add-host=my.gitea.url:host-gateway).