add comments to everything potentially consumer facing (#3127)

* add comments to everything potentially consumer facing

* rework smtp

---------

Co-authored-by: Aiden McClelland <3732071+dr-bonez@users.noreply.github.com>

sdk/base/lib/util/stringFromStdErrOut.ts

@@ -1,3 +1,10 @@
+/**
+ * Extracts a string result from a stdout/stderr pair.
+ * Returns `stdout` on success; rejects with `stderr` if it is non-empty.
+ *
+ * @param x - An object containing `stdout` and `stderr` strings
+ * @returns A promise resolving to `stdout`, or rejecting with `stderr`
+ */
 export async function stringFromStdErrOut(x: {
   stdout: string
   stderr: string