test: add tsd type tests for SemVerVersion/SemVerRange assignability

[gomesalexandre]

closes#73

Adds src/versions.test-d.ts, a tsd type-level test proving SemVerVersion and
SemVerRange (opaque/branded string types) aren't mutually assignable to each
other or to a plain string, following the existing .test-d.ts pattern
(hex.test-d.ts, json.test-d.ts, caip-types.test-d.ts, misc.test-d.ts).

Found while verifying: yarn test:types has been a silent no-op repo-wide

Not specific to this new file - every existing .test-d.ts file in the repo is
currently unreachable by yarn test:types. Root cause: tsd's auto-discovery
does typingsFile.replace(/\.d\.ts$/, '.test-d.ts') against package.json's
types field, which is ./dist/index.d.cts - the regex doesn't match .d.cts,
so the fallback to the configured "tsd": {"directory": "src"} glob never fires.
Instead globby matches the literal (post-build) ./dist/index.d.cts path,
finds one file containing zero assertions, and tsd reports a clean pass on
nothing.

One-line repro: append any bogus assertion to an existing *.test-d.ts file
(e.g. expectAssignable<Hex>(12345); in hex.test-d.ts) and yarn test:types
still exits 0.

Fixed in the same PR by pointing the script at the src glob explicitly:
"test:types": "tsd --files 'src/**/*.test-d.ts'". Verified against all 5
existing test-d files (hex, json, caip-types, misc, versions) - clean pass with
the fix, and the bogus-assertion mutation now correctly fails. Zero-risk to CI:
none of the 5 existing files have latent failures the broken discovery was
masking.

Happy to split this into two PRs (test file / script fix) if you'd prefer, but
shipping the test file alone would mean shipping code CI never actually runs, so
I bundled them.

Testing

Mutation-tested the new test file itself: inverted all 6 assertions
(expectAssignable/expectNotAssignable swapped), confirmed tsd catches
every one with a precise brand-mismatch diagnostic, reverted, confirmed clean.
Full jest suite and tsc --noEmit unaffected (7 pre-existing unrelated errors
in node_modules/web3-* typings, confirmed via stash comparison against
unmodified main). eslint clean.

---

Note

Low Risk
Test-only and script wiring changes with no runtime or public API impact.

Overview
Adds src/versions.test-d.ts so CI checks that SemVerVersion and SemVerRange stay distinct branded strings: values narrowed via assertIsSemVerVersion / assertIsSemVerRange assign to their own types, the two types are not interchangeable, and raw strings are not assignable without those assertions.

Updates test:types from plain tsd to tsd --files 'src/**/*.test-d.ts' because discovery against package.json’s types field (./dist/index.d.cts) never matched .test-d.ts, so type tests (including existing hex, json, etc.) were not actually executed.

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