feat: add archived repo filter

[densfox]

Changes

---

• Added --exclude-archived CLI flag to exclude archived repositories before SBOM collection.
• Wired excludeArchived through CollectorOptions into SbomCollector.
• Applied filtering in org repo listing (GET /orgs/{org}/repos) so archived repos are skipped before
  queuing fetches.
• Updated README argument reference for --exclude-archived.
• Updated changelog entry for this feature (0.2.1).
• Added test coverage for both paths:
  • flag off: archived + non-archived repos processed
  • flag on: archived repos excluded
• Wired new test into npm test script.

Usage

---

From code:

    const collector = new SbomCollector({
    token: process.env.GITHUB_TOKEN,
    org: "my-org",
    syncSboms: true,
    excludeArchived: true
  });

From CLI:

  github-sbom-toolkit --org my-org --sync-sboms --exclude-archived --sbom-cache sboms --token
  $GITHUB_TOKEN

Default behavior is unchanged: if --exclude-archived is not set, all listed repositories are processed
as before.

Test uses local mock/monkey-patch pattern to keep production code surface unchanged in this PR.

Build and test pass; lint issue is pre-existing repo-wide ESLint v9 config mismatch (.eslintrc vs flat
config).