POST /_journal/api/v1/images/alt writes the alt of a markdown post into
its source: the inline image  outside code
(classes.SetMarkdownImageAlt) or a raw img outside code
(classes.SetImageAltOutsideCode), so the next content save keeps it. An
image the markdown does not hold that way is refused with 422
changes.N.src and nothing is written.
ConvertContentH1 rewrites content only when it is HTML; a markdown
source, its code samples included, is kept byte for byte and only its
rendered content_html is converted, on API saves, imports,
journal:fix-headings and translations. ConvertH1 and SetImageAlt keep
the bytes of an unfinished tag at the end of the input.
- POST /_journal/api/v1/images/alt {dry_run, changes} sets alt on the
matching img of default or translated content through the tokenizer,
all or nothing (422), with a RecordSaved per changed post
- MCP journal_get_settings, journal_update_settings, journal_fix_headings
(manage_settings) and journal_set_image_alt (access_posts, destructive)
- journal:fix-headings help names its output and the refusal
