Rename grapho to pal, add onboard command, fix interactive input

- Rename grapho → pal across entire codebase (CLI, NixOS module,
  flake, docs, config paths)
- Add `pal onboard` interactive setup wizard with 4 steps:
  device, config repo, sync, backups
- Shows current setup summary when re-running onboard on an
  existing installation with warnings about what will change
- Fix askConfirm/askInput to read from /dev/tty so interactive
  prompts work correctly
- Remove || operator usage in askConfirm (not reliable in Lux)
- Add pal package to nix develop shell
- Document ~/.config/pal/ directory structure in README

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/MARKDOWN-EDITORS.md

@@ -1,6 +1,6 @@
-# Markdown Editors for grapho
+# Markdown Editors for pal
 
-This document covers recommended markdown editors for use with grapho across desktop and mobile platforms.
+This document covers recommended markdown editors for use with pal across desktop and mobile platforms.
 
 ## Recommended: md (PWA)
 
@@ -19,7 +19,7 @@ A lightweight, browser-based markdown editor that works on both desktop and mobi
 - Syntax highlighting for code blocks
 - Keyboard shortcuts (Ctrl+S to download, Ctrl+B/I for formatting)
 
-### Why It's Good for grapho
+### Why It's Good for pal
 - Works on any device with a browser
 - Can be installed as a PWA on mobile home screen
 - No account required
@@ -156,7 +156,7 @@ The best open-source markdown editor for Android.
 - Supports markdown, todo.txt, and more
 - Offline-first
 
-**Best for:** grapho users on Android.
+**Best for:** pal users on Android.
 
 ### iA Writer (iOS/Android)
 **Paid** | [Website](https://ia.net/writer)
@@ -187,12 +187,12 @@ Mobile companion to Obsidian desktop.
 
 ---
 
-## Recommendation for grapho Users
+## Recommendation for pal Users
 
 ### Simple Setup (Recommended)
 1. **Desktop:** MarkText or VS Code
 2. **Mobile:** md PWA (https://md-ashy.vercel.app) or Markor (Android)
-3. **Sync:** Syncthing (already part of grapho)
+3. **Sync:** Syncthing (already part of pal)
 
 ### Power User Setup
 1. **Desktop:** Obsidian with Syncthing sync
@@ -206,7 +206,7 @@ Mobile companion to Obsidian desktop.
 
 ---
 
-## Integration with grapho
+## Integration with pal
 
 All recommended editors work with plain markdown files, which means:
 
@@ -225,7 +225,7 @@ marktext ~/.nb/home/meeting-notes.md
 
 # Or on mobile, open the same file via Syncthing folder
 # Sync happens automatically
-grapho sync
+pal sync
 ```
 
 ## Sources