Replace boilerplate README with contributor-facing overview

[lwwmanning]

Summary

Replaces the stock create-next-app boilerplate README.md (which had been sitting unmodified since the repo was scaffolded) with a contributor-facing doc covering:

• What this repo is — one-paragraph intro: marketing site for Vortex, with a pointer to the Vortex format itself at github.com/vortex-data/vortex.
• Local development — Bun + Node prerequisites, clone / install / dev one-liner.
• Scripts — table of every bun run * script with a one-line description, including the gotcha that typecheck must run after build (velite needs .velite/ and Next emits next-env.d.ts during the build).
• CI flow — one line summarizing the order of CI steps with links to the workflow files.
• Contributing — the DCO sign-off requirement (git commit -s), DCO probot enforcement note, plus pointers to CLAUDE.md for architectural context.

The DCO mention is the load-bearing piece for an LF project: outside contributors landing on the repo cold need to know that an unsigned commit will be rejected at PR time, with the exact git commit -s to use.

Out of scope

• LICENSE file — package.json has no license field and the repo has no LICENSE at root. LF projects typically use Apache-2.0 but the choice belongs with the project's governance, not this PR. Worth a follow-up if it isn't intentional.
• CONTRIBUTING.md / CODE_OF_CONDUCT.md — common LF additions; can land separately once the README is in place.

Test plan

• CI green
• README renders cleanly on the GitHub repo page (table, links resolve, code blocks formatted)
• Vercel preview deploys (README change shouldn't affect the build, but confirms nothing breaks)

🤖 Generated with Claude Code

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
vortex	Ready	Preview, Comment	May 4, 2026 7:58pm

[github-actions]

🔦 Lighthouse audit

URL	Perf	A11y	Best practices	SEO	Report
/	🟢 99	🟢 100	🟢 96	🟢 100	report
/blog	🟢 100	🟢 100	🟢 96	🟢 100	report
/blog/btrblocks-compressor	🟢 100	🟢 96	🟢 96	🟢 100	report

Run 25340382315 · 2026-05-04 19:59 UTC