Automatically at NX Start up

NX loads all application libraries under the startup directory (custom root dir) at NX load: internal libraries first, then custom startup libraries, then immediately executes the standard entry point for each. Per-language entry points:

Language	Signature
C/C++	int ufsta( void )
VB.NET	Function Startup() As Integer
Java	int startup(void)
Python	def startup(argc, args): return <number>

Custom code at startup should be restricted to methods on session objects (no active part yet) — e.g. registering part/UDO callbacks, registering dialog boxes. Startup is the recommended place when:

• Registering dialogs for menu bar/toolbar buttons, when customized .men files reference UI Styler or Block Styler dialogs (see "Dialog from Menu or Toolbar").
• Registering UDO callbacks (display/edit/update/delete etc. — specific to a UDO class).
• Registering part callbacks (Part Open/Close/Save/New etc.) so NX invokes the custom module on part actions.

Unloading: if the app registered part or UDO callbacks, it must only unload at termination (see "Unload Options") — matches our ufusr_ask_unload() → Session::LibraryUnloadOptionAtTermination pattern in ArchitectureTab.cpp.

Relevance to spine-panel-kit

Directly confirms our existing pattern: ufsta() in ArchitectureTab.cpp creates the resource-bar tab and registers the activation callback at NX startup, exactly per this doc's guidance. No changes indicated — this is corroboration, not a new finding.