Keep a Substack subtitle above the post

Substack puts a post's subtitle in <description> and leaves it out of
content:encoded, and body() took content:encoded alone, so the subtitle
was lost (a known gap in CLAUDE.md). A description is now shown above the
body, as <p><em>, when it is short plain text the body does not already
contain. Podcast feeds that repeat their notes in both, whole or cut short
with an ellipsis, are unchanged; the comparison is by words, since a tag
taken out of the body leaves stray spaces around punctuation.

Checked against Experimental History's feed (subtitles appear) and The
Daily's (notes in both fields, shown once). Entries are inserted with ON
CONFLICT DO NOTHING, so only posts first seen from now on get it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CLAUDE.md

@@ -185,8 +185,6 @@ Deliberate simplifications get a `ponytail:` comment naming the ceiling and the
 
 * Cloudflare's `Cf-Access-Jwt-Assertion` is not verified — ipx trusts the hop plus `trusted_proxies`
   (documented in [docs/sso.md](docs/sso.md)).
-* A feed's `<description>` subtitle is dropped whenever `content:encoded` exists, which loses
-  Substack-style subtitles.
 
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