[agent] type-check the node test files (1,186 errors across 105 files)

[tyler-dane]

Goal / finish line

bun run type-check:tests (root tsconfig.tests.json, added with the verify-verdict PR) reports zero errors, and tsconfig.typecheck.json references it so bun run type-check covers every test file in core, backend, sync, and scripts.

Acceptance

• bun run type-check exits 0 with tsconfig.tests.json in its references.
• bun run type-check:tests is deleted (folded into type-check).
• No test was weakened or deleted to get there; fixes are typings, fixtures, and helper signatures.

Context

Until now the build graph excluded **/*.test.ts and **/__tests__/** for the node packages, so about 60,000 lines of tests were never type-checked. With Bun's test globals typed (bun-types/test-globals) the remaining errors are real: 420 TS2322 (wrong fixture shapes, often branded TimeZone/DateOnly strings), 173 TS2769, 117 TS4111 (index-signature access on env/config objects), 101 TS2532, 91 TS2741. The heaviest files: packages/sync/src/domain/provider-command.service.db.test.ts (135), packages/sync/src/storage/repositories/event.repository.db.test.ts (77), packages/sync/src/domain/cloud-command.service.db.test.ts (75), packages/backend/src/common/middleware/supertokens.middleware.test.ts (63).

Split by package (core, backend, sync/domain, sync/storage, sync/providers, scripts) so each PR stays inside the merge-guard rails. A shared fixture factory for branded types will remove most TS2322 hits at once.

Package scope

core, backend, sync, scripts

Verify commands

bun run type-check:tests
bun test:core
bun test:backend
bun test:sync
bun test:scripts

Approval boundary

allow

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