2.x — vision (history slot)

Per-era vision record for the 2.x architecture track. This is part of the versioned history beneath the living architecture (see ../../README.md for the boundary and decay rules).

This slot exists so the decay path has a home: when a piece of the living top-level architecture (docs/architecture/vision/, docs/architecture/diagrams/) is no longer current or future, it is demoted into the matching vision/ directory of its era — history accrues by version, nothing is deleted.

Empty until a living vision artifact decays into the 2.x era.