Ship pre-compiled JS to avoid transpilation cost

[JosXa]

Summary

• Ship pre-compiled JS in the npm package so consumers don't pay Bun transpilation cost on every load
• Follows the same pattern as opencode-snippets: tsc -p tsconfig.build.json emits to dist/, npm package ships only dist/
• Fix import.meta.dir path resolution for static file serving when running from dist/

Changes

• tsconfig.build.json — build config targeting dist/, with rewriteRelativeImportExtensions for Bun-style .ts imports
• package.json — main/types/module point to dist/, new build:plugin script, prepublishOnly hook, files: ["dist"]
• src/web/server/handlers/static.ts — strip trailing /dist from resolved module dir so static assets resolve correctly from both source and compiled output