docs: README en français (README.fr.md) + sélecteur de langue

- ajoute une traduction française complète du README
- lien de langue (English ⇄ Français) en tête des deux fichiers
- corrige une référence résiduelle `npx git-arboretum` → `@johanleroy/git-arboretum`

README.md

@@ -6,6 +6,10 @@
   A self-hosted web dashboard for your git worktrees and the Claude Code sessions running on them — from any device.
 </p>
 
+<p align="center">
+  <strong>English</strong> · <a href="README.fr.md">Français</a>
+</p>
+
 **Status: MVP.** The worktree-first dashboard, session discovery & resume, multi-repo worktree lifecycle, live session states, the web terminal, and mobile supervision (installable PWA, Web Push when a session needs you, approve/deny without opening a terminal) are implemented and tested.
 
 ---
@@ -20,7 +24,7 @@ Working with AI coding agents changed how we use git: one feature = one worktree
 
 ## What Arboretum does
 
-A single Node.js daemon you run on your dev machine (`npx git-arboretum`), serving a web UI usable from your desktop, phone or tablet:
+A single Node.js daemon you run on your dev machine (`npx @johanleroy/git-arboretum`), serving a web UI usable from your desktop, phone or tablet:
 
 - **Worktree-first, multi-repo dashboard** — every worktree of every registered repo, with its git state (branch, ahead/behind, dirty files) *and* the state of its Claude Code session (busy / waiting for input / idle / resumable).
 - **Full worktree lifecycle** — create (with per-repo post-create hooks: `npm ci`, copy `.env`…), adopt worktrees created by hand, delete with guardrails, prune orphans.