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/directory.html

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+<h1>The directory</h1>
+    <p>The directory gathers the public podcasts that iPX servers' listeners follow, and how many follow each. It never holds a file and never learns who listens.</p>
+
+    <h2>Browsing it</h2>
+    <p>Anyone can browse <a href="https://directory.ipxreader.app">directory.ipxreader.app</a> without signing in: the most followed, the categories, everything A to Z, and a page for each podcast with its latest episodes and its address, to subscribe to in any podcast app.</p>
+
+    <h2>Connecting your iPX</h2>
+    <p>In iPX, an admin opens Admin, Directory and enters the directory's address, <code>https://directory.ipxreader.app</code>, and the token its operator gave your server. Everyone on your server then has the Directory at the top of their list, and subscribes from it in one click.</p>
+    <p>Turn on sharing to add your server's podcasts to it. iPX sends only the podcasts' addresses and how many people on your server follow each, never who. It leaves out anything that looks private: a podcast someone marked Private, one with a login or a key in its address, and paid feeds such as Patreon's.</p>
+
+    <h2>Its API</h2>
+    <p>Anything the pages show, a program can read through the directory's API with a token: see the <a href="/docs/api/directory/">ipx-directory API reference</a>.</p>
+
+    <h2>Running your own</h2>
+    <p>The directory is in the same repository. Build it, give it a database (Postgres or SQLite) and a config file, and make a token for each server that will use it:</p>
+<pre><code>docker build -f Dockerfile.directory -t ipx-directory .</code></pre>
+<pre><code>services:
+  ipx-directory:
+    image: ipx-directory
+    container_name: ipx-directory
+    restart: unless-stopped
+    environment:
+      DIRECTORY_DATABASE_URL: "postgres://ipx_directory:password@db-host:5432/ipx_directory"
+    ports:
+      - "8100:8100"
+    volumes:
+      - ./directory:/config:ro   # directory.toml</code></pre>
+<pre><code># directory/directory.toml
+bind = "0.0.0.0:8100"
+database_url_env = "DIRECTORY_DATABASE_URL"</code></pre>
+<pre><code>docker exec ipx-directory ipx-directory token new my-server --access rw</code></pre>
+    <p>That prints the token, to give to the server, and the lines to add to <code>directory.toml</code>, which keeps only its SHA-256. The directory reads the file again within a minute, so adding or revoking a token needs no restart. It checks each podcast every six hours.</p>