chore: update deps

- native ES modules: type=module, exports map, explicit .js import
  extensions, engines node >=22.12.0
- TypeScript 7 (tsgo) with es2024 target, nodenext resolution,
  verbatimModuleSyntax and explicit types: [node]
- tests migrated from mocha/chai/nyc to node:test + node:assert/strict
  with built-in coverage (test-coverage / test-lcov scripts)
- lint/format switched from eslint to oxlint + oxfmt
- dev dependencies reduced to @types/node, oxlint, oxfmt, typescript
- @types/node moved out of runtime dependencies
- version bumped to 3.0.0

The migration commit had pre-set 3.0.0, which would make the usual
'npm version major' release flow skip to 4.0.0. Align back to the
published 2.0.1 so the release flow itself produces 3.0.0 with its tag
and commit.

- ip-regex -> node:net isIP/isIPv4/isIPv6 (verified identical behavior,
  including zone-id acceptance on IPv6)
- bigint-buffer -> local little-endian bigint<->buffer helpers
  (src/bigint-le.ts, exported from the barrel); the package is an
  abandoned addon whose prebuilt bindings fail to load on modern Node,
  printing a stderr warning and silently falling back to JS anyway

The package now has zero runtime dependencies.

Master's 2.0.1 release replaced the vulnerable bigint-buffer package
with a local src/bigint-buffer implementation - the v3 branch had done
the same independently (src/bigint-le). Resolution keeps master's
implementation (stricter: validates size, sign and overflow) under the
v3 ESM layout: explicit .js import extensions, spec files importing via
the package barrel, and the v3 dependency-free package.json.