ci: --allow-same-version on publish; drop npm@latest upgrade in tests

* publish.yml — `npm version` now passes `--allow-same-version` so a
  tag matching the package.json version (e.g. re-triggering the same
  release) doesn't error with "Version not changed".
* node.yml — drop `npm install -g npm@latest`. It broke on Node 22
  with `Cannot find module 'promise-retry'` after the global install.
  The npm bundled with Node 20/22/24 is fine for `npm test`; the
  upgrade is only needed where provenance support matters (the publish
  job, which runs on Node 24 with a sufficiently recent bundled npm).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: DavertMik

.github/workflows/node.yml

@@ -24,6 +24,5 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
-      - run: npm install -g npm@latest
       - run: npm install
       - run: npm test

.github/workflows/publish.yml

@@ -41,7 +41,7 @@ jobs:
       - run: npm install
 
       - name: Set package version from release tag
-        run: npm version "${{ github.event.release.tag_name }}" --no-git-tag-version
+        run: npm version "${{ github.event.release.tag_name }}" --no-git-tag-version --allow-same-version
 
       - name: Publish to npm
         run: |