TS misc (incremental)

[turadg]

refs: #5760

Description

Exploration of tightening up TS to speed up typechecking, for AI pair coding productivity.

This has a bunch of cleanups found while experimenting with composite projects, but this PR doesn't make that change.

The main DX change is the AGENTS.md directive to use yarn run -T tsc --noEmit --incremental for fast type checking. Example improvement,

❯ time yarn lint:types
yarn lint:types  9.77s user 0.39s system 199% cpu 5.078 total

❯ time yarn run -T tsc --noEmit --incremental
yarn run -T tsc --noEmit --incremental  2.46s user 0.19s system 208% cpu 1.272 total

Security Considerations

n/a

Scaling Considerations

n/a

Documentation Considerations

per se

Testing Considerations

CI

Upgrade Considerations

n/a