fix: support multiple bind_default_trigger calls

Previously trigger_action_name + trigger_widget_id were module-local
scalars, so the second bind_default_trigger call overwrote the first
(and reused the action name 'panel_toggle' so lib-core.input's binding
was also clobbered). Switched to a triggers array; each binding gets
a unique input action 'panel_toggle_<widget_id>' so multiple widgets
can be toggled by their own keys independently.

manifest.lib

@@ -1 +1 @@
-{"id":"lib-core.panel","version":"0.1.0","api_min":"0.1","deps":[]}
+{"id":"lib-core.panel","version":"0.1.1","api_min":"0.1","deps":[]}