test: prove the documented examples against the binary (#15)

* test: prove the documented examples against the binary

The README, the website and the shipped SKILL.md all promise specific
records, keys and exit codes, and nothing was checking that the binary
still agrees. Cover the claims that were unverified: the eleven
credential-free commands, the one-day bound on every wait, the config
directory relocation, `serve` refusing to run without a listener, the
four action commands that answer with an exit code alone, the search
filters, `--password-stdin`, `room listen`'s join records, and every
`--json` field the docs name for search, browse, whoami, user, shares,
room, download, serve and portmap.

The library README's examples now compile as doctests: lib.rs includes
it as the crate docs and the fences are `no_run`, so a signature change
cannot leave the advertised usage stale.

Two things were wrong. SKILL.md listed `queued` as a `serve` upload
status, which `upload_record` never emits — an agent branching on it
would wait for a state that never arrives. And the library README still
pointed at the 7.x lib.

* test: cover the completions commands the docs now advertise

soulseek-rs/src/SKILL.md

@@ -81,7 +81,7 @@ credentials and connection work.
 
 **`serve`** — stay online sharing files, one object per upload change: `user`,
 `path`, `size`, `bytes_sent`, `speed`, `status`
-(`queued`/`uploading`/`completed`/`cancelled`/`failed`), `reason`.
+(`uploading`/`completed`/`cancelled`/`failed`), `reason`.
 
 **`shares list`** — one object per configured folder: `directory`, `usable`.
 **`shares add <directory>`** and **`shares remove <directory>`** — change the