Add trusted gem publishing

.github/workflows/release.yml

@@ -0,0 +1,23 @@
+name: Push gem
+
+on:
+  push:
+    tags:
+      - "v*"
+
+jobs:
+  push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      id-token: write
+    environment: release
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          persist-credentials: false
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ruby
+          bundler-cache: true
+      - uses: rubygems/release-gem@v1

README.md

@@ -33,6 +33,10 @@ During the alpha series both gems are pinned in lockstep. Version 0.0.1.alpha6
 uses a subscribe-ready-before-prompt transport contract and reconnects an
 accepted turn without posting its prompt again.
 
+Releases use RubyGems trusted publishing. Register `release.yml` as the gem's
+trusted publisher (using the `release` environment); after that, a `v*` tag
+publishes without a long-lived RubyGems API key.
+
 ## Quickstart
 
 ```ruby