feat: CI build artifacts on PR + report npm version after release

[ranxianglei]

What

New GitHub Actions workflow that builds dist/ and uploads an installable artifact on every PR to master.

Why

Users have no easy way to test PR changes locally. This workflow:

1. Builds dist/ on each PR (same as the existing build job in ci.yml)
2. Creates tarball via npm pack — includes dist/, README.md, LICENSE, NOTICE
3. Uploads as artifact (30-day retention) — downloadable from the PR page
4. Comments on PR with two install options (updated idempotently on each push)

Also adds "prepare": "npm run build" to package.json — enables opencode plugin "github:ranxianglei/opencode-acp#branch" --global which auto-builds dist/.

Install Options for Testers

Option A — Install from GitHub (recommended):

opencode plugin "github:ranxianglei/opencode-acp#2026-08-13_pr-build-artifact" --global

Option B — Download artifact:

1. Download the artifact from the CI run (Actions tab)
2. Extract the tarball and copy dist/ to the plugin cache
3. Restart opencode

Files Changed

• .github/workflows/pr-artifact.yml (new) — workflow definition
• package.json — added prepare script
• devlog/2026-08-13_pr-build-artifact/ — REQ.md + WORKLOG.md

[github-actions]

📦 Built Plugin Artifact

Branch: 2026-08-13_pr-build-artifact (6f1c96e)

Option A — Install from npm PR tag (recommended)

opencode plugin opencode-acp@pr-298 --global

Each push to this PR publishes a new version under the pr-298 npm tag.

Option B — Install from GitHub

opencode plugin "github:ranxianglei/opencode-acp#2026-08-13_pr-build-artifact" --global

Option C — Download artifact

1. Download the artifact from the Actions run
2. Extract the tarball and install:

tar xzf opencode-acp-pr298.tgz
cp -r package/dist ~/.cache/opencode/packages/opencode-acp@latest/node_modules/opencode-acp/dist

3. Restart opencode to pick up changes.

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This comment is automatically updated on each push.