Each top-level tests/*.rs was its own crate → its own binary, each
statically linking the bundled engine + every dep. 26 of them, so an
edit to the lib relinked all 26. Moved the 25 standalone files into
tests/it/ under one tests/it/main.rs (the pattern typing_surface
already uses); cargo auto-detects it as the `it` target. End state: 2
integration-test binaries instead of 26.
Result: target/debug/deps 1.5 GB → 629 MB (-58%). Build time barely
moved (clean 22.9s→22.4s, lib-edit relink 13.3s→12.4s) — wall-clock is
dominated by compiling, not linking, so this is a disk win, not a speed
win (see docs/plans/20260602-test-consolidation.md). Tests unchanged at
2151/0/1; clippy clean; no fixups needed. typing_surface_matrix stays
its own already-consolidated binary.
Tradeoff: the 25 files now share one crate (a compile error fails the
whole `it` binary; module-scoped namespaces, no clashes) — negligible
for a solo project.