Document the automated release process

RELEASING.md

@@ -0,0 +1,29 @@
+# Releasing
+
+Releases are created by the manual **Release** GitHub Actions workflow.
+
+1. Update the version in `package.json` and `package-lock.json`:
+
+   ```bash
+   npm version 2.0.1 --no-git-tag-version
+   ```
+
+2. Install dependencies and verify the action:
+
+   ```bash
+   npm ci
+   npm run verify
+   ```
+
+3. Commit the version change in a pull request and merge it into `main`.
+
+4. Open **Actions → Release → Run workflow**, select `main`, and enter the
+   version without a leading `v`, such as `2.0.1`.
+
+The workflow verifies that the requested version matches `package.json`, runs
+the full test and build checks, creates the immutable version tag and GitHub
+Release, and advances the matching major-version tag. For example, releasing
+`2.0.1` creates `v2.0.1` and moves `v2` to the same commit.
+
+The workflow can safely be retried for the same version and commit. It fails if
+the requested version tag already points to another commit.