Future: what does not exist yet

The to-build list, split along the codebase's own boundary:

• backlog-core.md: core and infrastructure.
• backlog-light.md: the light domain, drivers, effects, sensors.
• backlog-mixed.md: items where a core mechanism meets a light one.

The analyses beside them survey a problem before it is planned: read when planning, not otherwise.

An item leaves here when it becomes a plan in present, and a shipped item is deleted rather than marked done. Tags in titles: (investigation) needs measurement first, (deferred) waits on a prerequisite, (future) is directional.