ci: publish @redsentech/lean-harness to GitHub Packages

- Rename npm package scope @redsen -> @redsentech (GitHub Packages
  requires the scope to match the owning org/user login).
- Add publishConfig.registry pointing at npm.pkg.github.com.
- Add .github/workflows/publish.yml: on push of a vX.Y.Z tag (or manual
  dispatch), runs validate + test, checks the tag matches
  package.json's version, then npm publish using the auto-issued
  GITHUB_TOKEN (packages: write permission, no secret to manage).
- Update README/QUICKSTART lh-CLI install instructions for the private,
  org-scoped registry (.npmrc scope + auth token setup).
- Verified locally with npm publish --dry-run: 68 files, correct
  registry target, correct tarball contents.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

docs/QUICKSTART.md

@@ -43,9 +43,9 @@ Use this when: you're a day-to-day Copilot CLI user who wants the harness availa
 multiple projects and doesn't need to modify the harness itself.
 
 Limitation: this installs the *behaviour* layer only. You still need `lh` on `PATH` (see
-below) for `lh init`/`lh doctor` and everything the agents call automatically — the package
-isn't on the npm registry yet, so today that means step B or C, not `npm install -g` (the
-README's `npm install -g @redsen/lean-harness` line is the path once it's published).
+below) — either `npm install -g @redsentech/lean-harness` from GitHub Packages (once you've
+pointed the `@redsentech` scope at it, see [The `lh` CLI](../README.md#the-lh-cli)), or step
+B/C below.
 
 ### B. Bootstrap an existing repo with the onboarding script