tools.claude: switch to permission-mode auto, drop GouvernAI
The built-in `auto` permission mode uses a classifier to gate per-action
approvals — covers the routine-action auto-approve role GouvernAI was
filling. Drops --dangerously-skip-permissions (no longer needed since
the mode handles approvals) and the GouvernAI plugin + fetchFromGitHub.
Sets permissions.defaultMode = "auto" in the wrapper's --settings so
every session boots into auto mode without a CLI flag.