feat: major dotfiles refactor with documentation and multi-platform improvements

- Add comprehensive CLAUDE.md with chezmoi best practices and AI assistant guidelines
- Restructure TODO.md with prioritized tasks and detailed organization
- Add PowerShell profile template for Windows platform support
- Split git configs into identity-specific templates (ryan/xevion)
- Convert nushell env.nu and gitconfig to templates for cross-platform rendering
- Refactor chezmoi hooks to TypeScript (.init_pre.ts, .update_pre.ts)
- Update .chezmoiignore with better platform-specific file handling
- Remove deprecated shellchecker.sh and tasks.json from VS Code config
- Add mise integration to shell configs (bash, zsh, nushell, PowerShell)
- Clean up commonrc.sh.tmpl WSL-specific code
- Disable Deno in VS Code settings, enable simple dialog mode
- Add nushell extension recommendation to VS Code

This commit establishes better cross-platform support (Windows/WSL/Linux),
improves documentation for future maintenance, and standardizes configuration
management patterns across the repository.

home/dot_config/nushell/config.nu.tmpl

@@ -896,4 +896,20 @@ $env.config = {
             event: { edit: selectall }
         }
     ]
+}
+
+# mise - polyglot tool version manager
+# Activates mise if installed (provides tools like vault, node, python, etc.)
+# This adds mise-managed tool paths to $env.PATH dynamically based on the current directory
+if (which mise | is-not-empty) {
+    $env.MISE_SHELL = "nu"
+
+    # Create the mise activation directory if it doesn't exist
+    let mise_cache = $"($nu.data-dir)/mise"
+    mkdir $mise_cache
+
+    # Run mise hook to setup environment for current directory
+    $env.PATH = ($env.PATH | split row (char esep))
+    mise hook-env -s nu | save --force $"($mise_cache)/hook-env.nu"
+    source $"($mise_cache)/hook-env.nu"
 }