feat: npm distribution

[dsherret]

Summary

Two changes bundled together because the npm publish steps land naturally on top of the gagen-generated workflow:

1. Convert ci.yml to gagen (ci.ts + ci.generated.yml)

Single-job structure preserved — still runs everything on macos-14 so dotnet can cross-compile every target. ci.ts has a #!/usr/bin/env -S deno run -A shebang and is 100755 in git so it can be invoked directly; the workflow lint step (./.github/workflows/ci.ts --lint) is wired in.

2. Publish an npm distribution of the plugin

Adds three scripts and the corresponding workflow steps so a tag push publishes @dprint/roslyn (main) plus seven per-platform sub-packages alongside the existing GitHub release.

• scripts/create_npm_packages.ts — extracts each platform zip and uses the new packageContents option in @dprint/automation@0.11.3 to ship the whole directory as the per-platform sub-package. Necessary because roslyn is a self-contained .NET app — the executable references ~200 sibling DLLs and runtime files. Produces npm-dist/publish-manifest.json with the main tarball's sha256.
• scripts/publish_npm_packages.ts — reads the manifest, publishes sub-package tarballs first (so the main's optionalDependencies resolve) then the main. Uses --access public --provenance. Publishes the tarballs directly so npm uploads the exact bytes whose sha256 is in the main plugin.json.
• scripts/generate_release_notes.ts — bumped to @dprint/automation@0.11.3. When the manifest is present, appends an "Alternatively, run dprint config add npm:@dprint/roslyn" block under step 1, matching the existing prose style.

draft_release in ci.ts gets permissions: { contents: write, "id-token": write } so npm publish --provenance can do the OIDC handshake.

npm package layout

Matches the convention already in use by @dprint/exec:

• Main: @dprint/roslyn
• Per-platform sub-packages: @dprint/roslyn-<os>-<arch>[-<libc>], e.g. @dprint/roslyn-linux-x64-glibc, @dprint/roslyn-darwin-arm64, @dprint/roslyn-win32-x64. Each carries os/cpu/libc filters so npm only installs the matching one.

Test plan

• deno run -A .github/workflows/ci.ts --lint passes (idempotent generation).
• deno check clean on all four scripts and on ci.ts.
• End-to-end smoke via a manual bootstrap publish (outside this branch): extracted the actual 0.20.1 release zips, ran create_npm_packages.ts in WSL, inspected the resulting tarballs — 206 entries each (205 .NET files + package.json), executable mode is 0o755, all DLLs and runtimes/ files end up alongside the binary, and the sha256 of each tarball equals the per-platform checksum written into the main plugin.json.
• First-publish chicken-and-egg. None of the seven @dprint/roslyn-* sub-packages exist on npm yet, so npm trusted publishing can't be configured on them ahead of time. The first version needs to be published manually with a regular token; after that, configure the GitHub repo as trusted publisher on each package and subsequent tag-driven publishes go through OIDC.

Pre-merge notes

• The pre-existing README.md modification on main is unrelated and not part of this PR.
• Bumps @dprint/automation from 0.10.3 to 0.11.3 (latest) in create_plugin_file.ts-adjacent scripts. The existing create_plugin_file.ts is left on 0.10.3 since nothing requires it to be on the newer version — happy to bump it for consistency if you'd like.