Reddit blocked unauthenticated `.json` access, so the previous extractor
returned block pages or timed out on every thread. Switch to parsing
old.reddit.com's server-rendered HTML, which needs no API key or JS.
Fetch layer:
- Rewrite every Reddit host to old.reddit.com before fetching; drop all
`.json` URL handling and the JSON response parser.
Extraction (webclaw-core::reddit):
- New HTML parser producing a typed post + nested comment tree.
- Comments nest structurally (.comment > .child > .sitetable > .comment);
old.reddit omits a usable depth attribute, so the tree is walked
recursively. Bodies live in .entry > form > .usertext-body > .md.
- Post metadata: title, author, subreddit, score, comment count
(data-comments-count), self-vs-link (self class / self.* domain),
flair, self-text body.
- Comment scores read the .score.unvoted title (the displayed value, not
the ±1 vote-state siblings); hidden scores are None, not 0.
- Deleted comments are kept in place so their replies aren't orphaned;
"load more comments" stubs are skipped.
Markdown output:
- Reply nesting via blockquote depth (avoids 4-space indentation turning
text and code fences into broken indented-code blocks).
- Links keep their target as [text](url); root-relative reddit links
resolve against old.reddit.com. Nested lists indent correctly.
- A recognised but unparseable /comments/ page returns no content rather
than falling through to generic extraction of Reddit chrome.
Tests: regression suite runs against real old.reddit.com fixtures
(testdata/reddit/), the ground truth that surfaced the parsing and
markdown bugs synthetic HTML had hidden. Fixtures are excluded from the
published crate.
