(v1) Add root README.md for v1 branch GitHub landing page

[yamcodes]

Problem

The v1 branch root README.md is a 25-byte stub containing only packages/arkenv/README.md. GitHub renders this literally, so visitors to the v1 branch see useless text instead of a project landing page.

On main, the same stub exists but is less noticeable because packages/arkenv/README.md there is a full marketing README. On v1, that package README is CLI-focused dev documentation — making the GitHub landing page especially poor.

Desired behavior

Replace the root README.md on the v1 branch only with a full, inlined marketing-style README (same structure as main's packages/arkenv/README.md), adapted for v1:

• Install command: npx arkenv@latest init (and equivalent pnpm/yarn/bun variants)
• Alpha callout: Prominent note at the top linking to the v1 roadmap (#683)
• Doc links: Point to the alpha preview at https://arkenv-v1.vercel.app/docs/...
• Branch-aware URLs: CI badge (branch=v1), StackBlitz (tree/v1/...), GitHub blob links (blob/v1/...)
• Shared assets: Logo and demo GIF on arkenv.js.org can remain unchanged

Leave packages/arkenv/README.md unchanged — it serves as the npm package README and should stay CLI-focused.

Acceptance criteria

• Root README.md on v1 renders as a full GitHub landing page (not the stub text)
• Install commands use arkenv (not @arkenv/cli)
• Docs/FAQ/quickstart links point to arkenv-v1.vercel.app
• Alpha/pre-release callout references v1 Roadmap #683
• CI badge, StackBlitz, and GitHub blob links are branch-aware (v1)
• packages/arkenv/README.md is not modified
• main branch is not modified

Out of scope

• Fixing the root README stub on main (separate follow-up)
• Rewriting packages/arkenv/README.md
• Updating links to production after v1 ships — tracked in (v1) Update v1 README links from alpha preview to production on v1 launch #1306

Related

• v1 Roadmap #683 — v1 roadmap
• (v1) Update v1 README links from alpha preview to production on v1 launch #1306 — follow-up to update preview links to production on v1 launch

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[yamcodes]

This was generated by AI during triage.

Agent Brief

Category: enhancement
Summary: Replace the v1 branch root README stub with a full GitHub landing page adapted for the v1 alpha

Current behavior:
The root README.md on the v1 branch contains only the text packages/arkenv/README.md (a pointer stub). GitHub renders this literally, producing a useless landing page. The actual content in packages/arkenv/README.md on v1 is CLI-focused developer documentation, not a repo overview.

Desired behavior:
The root README.md on v1 should contain fully inlined markdown — the same marketing structure used on main's package README (logo, tagline, badges, install tabs, demo GIF, docs links, contributors section) — with v1-specific adaptations:

• Install commands use npx arkenv@latest init (and pnpm/yarn/bun equivalents), not @arkenv/cli
• An alpha/pre-release callout at the top links to #683
• Documentation links (Docs, FAQ, quickstart) point to https://arkenv-v1.vercel.app/docs/...
• Branch-aware links: CI test badge uses branch=v1, StackBlitz uses tree/v1/..., GitHub blob links use blob/v1/...
• Shared CDN assets (logo SVG, demo GIF on arkenv.js.org) remain unchanged
• packages/arkenv/README.md is left untouched (npm package README, CLI-focused)

Key interfaces:

• Root README.md on the v1 branch — replace stub with inlined marketing content
• packages/arkenv/README.md on v1 — source of install command pattern (npx arkenv@latest init); do not modify
• Main branch packages/arkenv/README.md — reference for marketing structure and content to adapt

Acceptance criteria:

• Visiting the repo on the v1 branch shows a rendered marketing landing page, not stub text
• All four install tabs (npm/pnpm/yarn/bun) use arkenv package name
• Docs, FAQ, and quickstart links resolve to arkenv-v1.vercel.app
• Alpha callout references the v1 roadmap (v1 Roadmap #683)
• CI badge, StackBlitz, and GitHub blob links reference the v1 branch
• packages/arkenv/README.md is unchanged
• No changes are made to main

Out of scope:

• Fixing the root README stub on main
• Modifying packages/arkenv/README.md
• Updating preview links to production URLs after launch ((v1) Update v1 README links from alpha preview to production on v1 launch #1306)