feat: add iCloud vault support and launcher command installation

- Add new /install-claudesidian-command to create shell alias for launching vault from anywhere
- Add automatic iCloud Drive vault detection in init-bootstrap
- Add iCloud-specific search path with maxdepth 5 for nested structure
- Add fallback prompt asking about iCloud if vault not found
- Update README with launcher command documentation and usage examples
- Shell command auto-resumes existing sessions or starts new ones

This addresses user feedback about iCloud vault detection and adds convenient
shell launcher similar to obsidian-cli pattern.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

README.md

@@ -152,6 +152,7 @@ Pre-configured AI assistants ready to use:
 - `de-ai-ify` - Remove AI writing patterns from text
 - `upgrade` - Update to the latest claudesidian version
 - `init-bootstrap` - Re-run the setup wizard
+- `install-claudesidian-command` - Install shell command to launch vault from anywhere
 
 Run with: `/[command-name]` in Claude Code
 
@@ -263,6 +264,31 @@ Run these with `pnpm`:
 
 ## Advanced Setup
 
+### Quick Launch from Anywhere
+
+Install a shell command to launch your vault from any directory:
+
+```bash
+# In Claude Code, run:
+/install-claudesidian-command
+```
+
+This creates a `claudesidian` alias that:
+- Changes to your vault directory automatically
+- Tries to resume your existing session (if one exists)
+- Falls back to starting a new session
+- Returns to your original directory when done
+
+**Usage:**
+```bash
+# From anywhere in your terminal:
+claudesidian
+
+# It will automatically resume your last session or start a new one
+```
+
+The command is added to your shell config (~/.zshrc, ~/.bashrc, etc.) so it persists across terminal sessions.
+
 ### Git Integration
 
 Initialize Git for version control: