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;