Lua API gaps that are generally useful, not just for accessibility

[aradix85]

Following up on discussion #8793 about a self-voicing accessibility layer for Bright Nights, I want to separate one specific question for the maintainers from the broader concept discussion there.
A handful of the Lua bindings that an accessibility mod would require appear to be generally useful for mod development, independent of accessibility:
• vehicle_part / vpart_info exposure. Currently the Lua API exposes wrapped_vehicle with pos and type, but the part-level data — mount points, installation requirements, part stats — is not reachable from Lua. A vehicle-balancing mod, an auto-repair mod, or a fuel-efficiency mod would all need this same data.
• Construction bindings. No construction-related types are currently exposed to Lua. Mods that want to add construction types, scripted blueprints, or build-automation can't do so today.
• An on_add_msg event hook in messages.cpp. Following BN's existing cata::run_hooks convention. Any mod that wants to react to in-game events currently has to poll the message stream, which is inefficient and can miss events between polls. An event-driven hook would benefit achievement mods, statistics mods, alarm mods — anything message-reactive.
I'm not offering to write these PRs myself. Raising this because filling these gaps would broaden what's possible across multiple mod types — accessibility being one, but vehicle balancing, automation, achievement-tracking, and statistics mods would all benefit. Whether and when this fits the maintainers' own roadmap is the question.
Greetings, Anouk,