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/reference/functions.md

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+# Library Functions
+
+Documentation for library functions available in m3ta-nixpkgs.
+
+## Overview
+
+The library provides helper functions for your NixOS and Home Manager configurations.
+
+## Available Libraries
+
+### `m3ta-lib.ports`
+
+Port management utilities for managing service ports across hosts.
+
+## Port Management Functions
+
+### `mkPortHelpers`
+
+Create port helper functions from a ports configuration.
+
+#### Signature
+
+```nix
+mkPortHelpers :: portsConfig -> portHelpers
+```
+
+#### Arguments
+
+`portsConfig` - An attribute set with structure:
+
+```nix
+{
+  ports = { service-name = port-number; ... };
+  hostPorts = { hostname = { service-name = port-number; ... }; ... };
+}
+```
+
+#### Returns
+
+An attribute set containing helper functions:
+
+```nix
+{
+  getPort = service: host -> port-number-or-null;
+  getHostPorts = host -> ports-attrs;
+  listServices = -> [string];
+}
+```
+
+#### Usage
+
+```nix
+{config, inputs, ...}: let
+  m3taLib = inputs.m3ta-nixpkgs.lib.${config.system};
+
+  myPorts = {
+    ports = {
+      nginx = 80;
+      grafana = 3000;
+    };
+    hostPorts = {
+      laptop = {
+        nginx = 8080;
+      };
+    };
+  };
+
+  portHelpers = m3taLib.ports.mkPortHelpers myPorts;
+in {
+  # Get port with host override
+  services.nginx.port = portHelpers.getPort "nginx" config.networking.hostName;
+
+  # Get all ports for host
+  laptopPorts = portHelpers.getHostPorts "laptop";
+
+  # List all services
+  allServices = portHelpers.listServices;
+}
+```
+
+### `getPort` (from portHelpers)
+
+Get port for a service, with optional host-specific override.
+
+#### Signature
+
+```nix
+getPort :: string -> string -> int-or-null
+```
+
+#### Arguments
+
+1. `service` - The service name (string)
+2. `host` - The hostname (string), or `null` for default
+
+#### Returns
+
+Port number (int) or `null` if service not found.
+
+#### Usage
+
+```nix
+services.nginx = {
+  port = portHelpers.getPort "nginx" "laptop";  # Returns host-specific port
+  # or
+  port = portHelpers.getPort "nginx" null;     # Returns default port
+};
+```
+
+### `getHostPorts` (from portHelpers)
+
+Get all ports for a specific host (merges defaults with host overrides).
+
+#### Signature
+
+```nix
+getHostPorts :: string -> attrs
+```
+
+#### Arguments
+
+1. `host` - The hostname (string)
+
+#### Returns
+
+Attribute set of all ports for the host.
+
+#### Usage
+
+```nix
+laptopPorts = portHelpers.getHostPorts "laptop";
+# Returns: { nginx = 8080; grafana = 3000; prometheus = 9090; ... }
+```
+
+### `listServices` (from portHelpers)
+
+List all defined service names.
+
+#### Signature
+
+```nix
+listServices :: -> [string]
+```
+
+#### Returns
+
+List of service names (strings).
+
+#### Usage
+
+```nix
+allServices = portHelpers.listServices;
+# Returns: ["nginx" "grafana" "prometheus" "homepage"]
+```
+
+### `getDefaultPort`
+
+Simple helper to get a port without host override.
+
+#### Signature
+
+```nix
+getDefaultPort :: portsConfig -> string -> int-or-null
+```
+
+#### Arguments
+
+1. `portsConfig` - Same structure as `mkPortHelpers`
+2. `service` - The service name (string)
+
+#### Returns
+
+Port number (int) or `null` if service not found.
+
+#### Usage
+
+```nix
+services.my-service = {
+  port = m3taLib.ports.getDefaultPort myPorts "my-service";
+};
+```
+
+## Using Library Functions
+
+### Importing
+
+```nix
+{config, inputs, ...}: let
+  # Import library
+  m3taLib = inputs.m3ta-nixpkgs.lib.${config.system};
+in {
+  # Use library functions
+}
+```
+
+### Example: Custom Port Management
+
+```nix
+{config, inputs, ...}: let
+  m3taLib = inputs.m3ta-nixpkgs.lib.${config.system};
+
+  myPorts = {
+    ports = {
+      web = 80;
+      api = 8080;
+      db = 5432;
+    };
+    hostPorts = {
+      dev = {
+        web = 8080;
+        api = 8081;
+      };
+    };
+  };
+
+  portHelpers = m3taLib.ports.mkPortHelpers myPorts;
+
+  hostname = config.networking.hostName;
+in {
+  services.nginx = {
+    enable = true;
+    virtualHosts.${hostname} = {
+      locations."/" = {
+        proxyPass = "http://localhost:${toString (portHelpers.getPort "api" hostname)}";
+      };
+    };
+  };
+
+  services.postgresql = {
+    enable = true;
+    port = portHelpers.getPort "db" hostname;
+  };
+}
+```
+
+### Example: Generate Config Files
+
+```nix
+{inputs, ...}: let
+  m3taLib = inputs.m3ta-nixpkgs.lib.${system};
+
+  myPorts = {
+    ports = {
+      service1 = 3000;
+      service2 = 3001;
+    };
+  };
+
+  portHelpers = m3taLib.ports.mkPortHelpers myPorts;
+in {
+  environment.etc."ports.toml".text = generators.toTOML {} {
+    services = portHelpers.getHostPorts "desktop";
+  };
+}
+```
+
+## Function Reference Summary
+
+| Function | Purpose | Return Type |
+|----------|---------|------------|
+| `mkPortHelpers` | Create port helper functions | `portHelpers` attrs |
+| `getPort` | Get port with optional host override | `int or null` |
+| `getHostPorts` | Get all ports for host | `attrs` |
+| `listServices` | List all service names | `[string]` |
+| `getDefaultPort` | Get default port only | `int or null` |
+
+## Related
+
+- [Port Management Guide](../guides/port-management.md) - Detailed usage guide
+- [NixOS Ports Module](../modules/nixos/ports.md) - Port management module
+- [Home Manager Ports Module](../modules/home-manager/ports.md) - User-level port management
+- [Architecture](../ARCHITECTURE.md) - Understanding library functions