Modernize release infrastructure

- Add tag-triggered publish workflow (npm publish via GitHub Actions OIDC)
- Remove Changelog.md in favor of GitHub Releases
- Remove AUTHORS.txt, .mailmap, and the update-authors script
- Add MAINTAINERS.md with releasing instructions and release notes style guide

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: domenic

.github/workflows/publish.yml

@@ -0,0 +1,22 @@
+name: Publish
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+permissions:
+  id-token: write
+  contents: read
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
+        with:
+          node-version: lts/*
+          registry-url: https://registry.npmjs.org
+      - run: npm ci
+      - run: npm publish