Docs: a page each, and API references for ipx and the directory laid out like docs.rs (#223)

site/gen.mjs writes them from site/api.mjs, which holds each endpoint and type as the handlers
have them, and site/docs.mjs, the guides. A misspelt type in api.mjs fails the build rather than
leaving a name that links nowhere.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

site/guides/cli.html

@@ -0,0 +1,22 @@
+<h1>The command line</h1>
+    <p>The same <code>ipx</code> program that runs the server is its command line. Run it in the container with <code>docker exec ipx ipx …</code>; when the server is running, it does the work and the command shows what happened.</p>
+    <div class="scroll"><table>
+      <thead><tr><th>Command</th><th>What it does</th></tr></thead>
+      <tbody>
+        <tr><td><code>ipx list</code></td><td>Every podcast and its state</td></tr>
+        <tr><td><code>ipx status</code></td><td>How many podcasts, how many files waiting and downloaded</td></tr>
+        <tr><td><code>ipx fetch [id] [--force]</code></td><td>Check everything that is due, or one podcast; <code>--force</code> checks it even if it is not due</td></tr>
+        <tr><td><code>ipx add &lt;url&gt;</code>, <code>ipx rm &lt;id&gt;</code></td><td>Add a podcast, or take it out</td></tr>
+        <tr><td><code>ipx import &lt;file&gt;</code>, <code>ipx export &lt;file&gt;</code></td><td>OPML in or out</td></tr>
+        <tr><td><code>ipx reap [--dry-run]</code></td><td>Clear old files now, to stay within the space you set</td></tr>
+        <tr><td><code>ipx user add|list|passwd|rm</code></td><td>Accounts</td></tr>
+      </tbody>
+    </table></div>
+    <h2>The control socket</h2>
+    <p>A program on the same machine can also talk to the running server over its control socket, one JSON command a line, and read back one event a line:</p>
+<pre><code>printf '{"cmd":"fetch","force":true}\n' | socat - UNIX-CONNECT:$XDG_RUNTIME_DIR/ipx.sock
+{"ev":"feed_start","feed":"atp"}
+{"ev":"download_done","feed":"atp","enclosure":42,"path":"…","bytes":3000000}
+{"ev":"feed_done","feed":"atp","new":1,"downloaded":1,"failed":0,"torrents":0}
+{"ev":"scan_done","feeds":1}</code></pre>
+    <p>The commands are <code>fetch</code> (optional <code>feed</code>, <code>force</code>), <code>download</code> (<code>enclosure</code>), <code>reap</code> (optional <code>dry_run</code>) and <code>status</code>.</p>