docs: add technical writing guide

modules/agents/pi/patches/pi-tool-lookup-validation.patch

@@ -7,6 +7,7 @@ diff --git a/packages/coding-agent/src/utils/tools-manager.ts b/packages/coding-
  		const result = spawnSync(cmd, ["--version"], { stdio: "pipe" });
 -		// Check for ENOENT error (command not found)
 -		return result.error === undefined || result.error === null;
++		// Downloaded generic Linux binaries can exist but fail on NixOS before they print a version.
 +		return (result.error === undefined || result.error === null) && result.status === 0;
  	} catch {
  		return false;

modules/nvim/nvim.nix

@@ -181,8 +181,8 @@ in
           };
         };
 
-        # gbprod/nord.nvim, set up in ./config.lua.
-        # nixvim's colorschemes.nord is a different plugin.
+        # `gbprod-nord` provides the `require("nord").setup()` API used in `./config.lua`.
+        # nixpkgs packages `shaunsingh/nord.nvim` as `nord-nvim`, which is a different plugin.
         extraPlugins = [ pkgs.vimPlugins.gbprod-nord ];
 
         extraConfigLua = builtins.readFile ./config.lua;