Document nginx compression for markdown/JSON transfers (AI)

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXSVPS3UmmASiiprPfcnUd

README.md

@@ -362,6 +362,31 @@ server {
 > `autoindex_format json` is ever lost (config drift, an older nginx), the crawler falls back
 > to parsing nginx's default HTML directory listing instead of breaking outright.
 
+### Compression
+
+Markdown and directory-listing JSON are both plain text, so gzip shrinks them well — and since
+the browser decompresses transparently, this needs no changes on the cmjs side. nginx doesn't
+know `.md` is text by default (it falls back to `application/octet-stream`, which `gzip_types`
+won't match), so map it explicitly and enable gzip for both content types:
+
+```nginx
+# in http {} or a shared mime block
+types {
+    text/markdown md;
+}
+
+# in http {} or the server block above
+gzip on;
+gzip_types text/markdown text/plain application/json;  # json covers the autoindex_format listings
+gzip_min_length 256;
+gzip_vary on;
+```
+
+Pre-compressing with `gzip_static` is possible but needs a `.md.gz` alongside every article, which
+is a build step this project deliberately has none of — plain runtime `gzip on` is the better fit
+here. Brotli usually compresses text better still, but needs the separate `ngx_brotli` module,
+not built into stock nginx — only worth it if you're already building custom nginx modules.
+
 ## Article discovery & caching
 
 Discovery happens in two phases. **Indexing** crawls `cmjs/articles/` client-side to build a