#3006: fix(scripts): use local pnpm binary in run-node.mjs if global is missing

## Summary - Use local pnpm binary from node_modules/.bin as a fallback when global pnpm is missing - Improves bootstrap reliability in restricted environments ## Testing - Not run (script change only) <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates `scripts/run-node.mjs` to prefer a local `pnpm` binary from `node_modules/.bin` when available, improving the reliability of the TypeScript build step in environments without a global pnpm install. The change affects the “dist is stale” build path that spawns pnpm to run the configured TS compiler before running the built entrypoint. <h3>Confidence Score: 4/5</h3> - Mostly safe to merge, but the intended pnpm fallback is currently ineffective on Windows. - Change is small and localized to the build-spawn path, but there is a functional gap on Windows where `cmd.exe /c pnpm ...` still requires a global pnpm and ignores the computed local pnpm path; non-Windows behavior should work as intended. - scripts/run-node.mjs (Windows spawn args) <!-- greptile_other_comments_section --> **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->