Register an "iwd" gadcon client; each instance carries an elm_icon
that swaps freedesktop standard names based on Iwd_State.
Click toggles the (still stubbed) popup. Listener on iwd_manager
refreshes every active instance on state changes.
E 0.27 only ships the legacy gadcon API (no e_gadget header), so
this targets gadcon for compatibility.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
