docs: update zellij-ps to reflect project switcher functionality

- Update package description and fix mainProgram typo
- Rewrite documentation to describe project switching, not process viewing
- Add PROJECT_FOLDERS configuration and usage examples
- Update all references across docs (README, guides, module overviews)

docs/modules/home-manager/cli/zellij-ps.md

@@ -0,0 +1,81 @@
+# zellij-ps Home Manager Module
+
+Zellij project switcher for Home Manager.
+
+## Overview
+
+This module configures the zellij-ps tool, a Fish script that provides a fast, interactive way to switch between project folders in Zellij terminal multiplexer sessions.
+
+## Quick Start
+
+```nix
+{config, ...}: {
+  imports = [m3ta-nixpkgs.homeManagerModules.default];
+
+  m3ta.cli.zellij-ps = {
+    enable = true;
+  };
+}
+```
+
+## Module Options
+
+### `m3ta.cli.zellij-ps.enable`
+
+Enable zellij-ps module.
+
+- Type: `boolean`
+- Default: `false`
+
+### `m3ta.cli.zellij-ps.package`
+
+Custom package to use.
+
+- Type: `package`
+- Default: `pkgs.zellij-ps`
+
+## Usage
+
+After enabling, zellij-ps will be available in your path:
+
+```bash
+# Run from outside Zellij to start a project session
+zellij-ps
+
+# Or pass a project path directly
+zellij-ps ~/projects/my-project
+```
+
+### Basic Usage
+
+1. Set `$PROJECT_FOLDERS` in your shell config (e.g., `~/projects:~/code`)
+2. Run `zellij-ps` from outside a Zellij session
+3. Use fzf to select a project from your configured folders
+4. Zellij will create or attach to a session for that project
+
+## Configuration
+
+### Custom Package
+
+Use a custom or modified package:
+
+```nix
+m3ta.cli.zellij-ps = {
+  enable = true;
+  package = pkgs.callPackage ./my-zellij-ps {};
+};
+```
+
+## Dependencies
+
+The module ensures these are installed:
+
+- `fish` - Shell for script execution
+- `fd` - Fast file search
+- `fzf` - Fuzzy finder
+- `zellij` - Terminal multiplexer
+
+## Related
+
+- [zellij-ps Package](../../packages/zellij-ps.md) - Package documentation
+- [Using Modules Guide](../../guides/using-modules.md) - Module usage patterns