* chore(ci): split unit and e2e tests into separate jobs

Reorganises tests to mirror apify/mcpc:

- Move pure unit tests to `test/unit/` (`tools.js`) and the
  network/server-backed tests to `test/e2e/`. Shared helpers stay in
  `test/utils/`. SSL fixtures move alongside the e2e tests.
- Add `test:unit` and `test:e2e` npm scripts; `npm test` still runs both
  suites under nyc with the `--insecure-http-parser` Node option that
  the e2e suite needs.
- Split the Check workflow into a `unit` job that runs the matrix
  (Node.js 20/22/24) on ubuntu-24.04 with `fail-fast: false` plus lint
  on Node.js 24, and a single `e2e` job that runs on Node.js 24 with
  the `localhost-test` hosts entry.

* chore(ci): extract lint into its own job

Per review on #651: the unit job ran lint on Node 24 only, which made
the job name misleading and coupled a lint failure to unit-test
reporting on that one matrix entry. Lint now runs as a dedicated job
alongside unit and e2e.

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Co-authored-by: Claude <noreply@anthropic.com>