OCaml HTML5 parser/serialiser based on Python's JustHTML

Fix build warnings and odoc documentation errors

- Add explicit unix library dependency to dune files (html5rw, tomlt)
- Fix odoc heading levels ({0 -> {1) in imap subject.mli and thread.mli
- Fix code block indentation in subject.mli and h2_stream.mli
- Change unresolved module references to plain text (Bytesrw_unix,
Bytesrw_eio, Webfinger.Jrd.t)
- Fix @raise tags to use Error instead of Error.t
- Escape @mention/@mentions text in poe docs to avoid unknown tag warnings
- Remove unreachable flag_perm rule and redundant list_mailbox production
from IMAP grammar

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

+9 -9
+1 -1
bin/dune
··· 2 2 (name html5check) 3 3 (public_name html5check) 4 4 (package html5rw) 5 - (libraries htmlrw_check html5rw bytesrw cmdliner)) 5 + (libraries htmlrw_check html5rw bytesrw cmdliner unix))
+8 -8
examples/dune
··· 1 1 (executable 2 2 (name basic_parsing) 3 3 (modules basic_parsing) 4 - (libraries bytesrw html5rw)) 4 + (libraries bytesrw html5rw unix)) 5 5 6 6 (executable 7 7 (name css_selectors) 8 8 (modules css_selectors) 9 - (libraries bytesrw html5rw)) 9 + (libraries bytesrw html5rw unix)) 10 10 11 11 (executable 12 12 (name dom_manipulation) 13 13 (modules dom_manipulation) 14 - (libraries bytesrw html5rw)) 14 + (libraries bytesrw html5rw unix)) 15 15 16 16 (executable 17 17 (name text_extraction) 18 18 (modules text_extraction) 19 - (libraries bytesrw html5rw)) 19 + (libraries bytesrw html5rw unix)) 20 20 21 21 (executable 22 22 (name error_handling) 23 23 (modules error_handling) 24 - (libraries bytesrw html5rw)) 24 + (libraries bytesrw html5rw unix)) 25 25 26 26 (executable 27 27 (name fragment_parsing) 28 28 (modules fragment_parsing) 29 - (libraries bytesrw html5rw)) 29 + (libraries bytesrw html5rw unix)) 30 30 31 31 (executable 32 32 (name encoding_detection) 33 33 (modules encoding_detection) 34 - (libraries bytesrw html5rw)) 34 + (libraries bytesrw html5rw unix)) 35 35 36 36 (executable 37 37 (name web_scraper) 38 38 (modules web_scraper) 39 - (libraries bytesrw html5rw)) 39 + (libraries bytesrw html5rw unix))