fix: make the tsd type tests actually run - #322

Top of stack #315, on #321.

yarn test:types runs bare tsd, which finds no test files at all. It produces no output and exits 0 regardless, so the 460 lines of type assertions across src/*.test-d.ts have not been checking anything.

Proof, before this change:

$ printf 'expectAssignable<Hex>(999);' >> src/hex.test-d.ts
$ yarn test:types
$ echo $?
0

Pointing tsd at the files explicitly reports it properly and exits 1:

✖  Argument of type 999 is not assignable to parameter of type `0x${string}`.

Cause

tsd resolves test files relative to the types field, which has pointed at ./dist/index.d.cts since ts-bridge was adopted in #182 (2024-04-23). tsd 0.29 does not resolve .d.cts, and the tsd.directory setting does not compensate. 26 releases have shipped since, all with this check silently passing.

Fix

- "test:types": "tsd"
+ "test:types": "tsd --files 'src/*.test-d.ts'"

Fixing the invocation rather than the types field, since the field is correct for consumers and only tsd is confused by it.

All four files pass once actually executed, so none of them needed changing. yarn test:types now exits 1 on a bad assertion and 0 when clean.

Relevance to the migration

This was found while working out what to do with tsd in Phase B, since core has no way to run it. Worth knowing the honest baseline before deciding: these assertions have been dormant for 17 months, so whatever we do with them in core, we are not losing coverage we currently have.