chore: improve incremental typecheck performance

[jlongster]

Summary

• add explicit variance annotations around the Effect Drizzle query graph
• enable persistent incremental metadata for Core's source and tests configs
• make Core source a declaration-emitting composite project consumed by the tests/scripts config
• make all direct Core dependents consume Core declarations through project references
• make internal migration, error, and plugin types portable for declaration emit

Performance

Measured in packages/core on Linux with 2 AMD EPYC 9554P cores and Bun 1.3.14:

Scenario	Before	After
clean check	9.10s	13.39s
unchanged check	1.09s	0.06s
Session implementation edit	10.21s	2.98s
provider adapter edit	about 10s	1.09s

The clean build is slower because it emits the Core declaration boundary. Normal edit/typecheck feedback is substantially faster because build mode can compare the source declaration signature and skip the downstream tests/scripts project when public types are unchanged.

The variance annotations independently reduced clean Core type instantiations by roughly 264k and improved the original clean median by about 3.9%.

TUI results:

Scenario	Before	After
normal check with Core declarations built	9.61s	2.73s
tiny TUI edit	9.18s	3.08s
fresh check including Core declaration build	9.61s	12.50s

The TUI program drops from 3,441 files to 1,988 files and resolves zero Core source files. Direct dependents use tsgo -b, which follows the Core reference and builds missing declarations automatically. Turbo explicitly orders the seven direct Core consumers after @opencode-ai/core#typecheck while leaving unrelated package typechecks independent.

Validation

• bun turbo typecheck --concurrency=1 (32/32 tasks passed)
• bun turbo typecheck --filter=@opencode-ai/tui --concurrency=1 --force
• standalone bun run typecheck in App, Enterprise, SDK Next, Server, Session UI, Simulation, and TUI
• focused instruction/session tests (40 passed)
• focused provider and database migration tests (28 passed)

[Brendonovich]

about time woohoo