feat(agents): darkwing host-dev launcher + entry-point consolidation

scripts/agent.sh --host-dev delegates to scripts/agent-host-dev.sh;
agents/darkwing/launch.sh provides the native development TUI
(context, skills, coding tools, /goal). Root SOUL.md is the M14-era
default-collaborator persona captured by the ACT-1 context work.
Launcher regression checks pass (test-darkwing-launch.mjs).

agents/darkwing/launch.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+# Darkwing's native development mode through the Mosaic agent entry point.
+set -euo pipefail
+REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+exec "$REPO/scripts/agent.sh" --host-dev darkwing "$@"