New callout features in @lossless-group/lfm

remark-callouts grew up: multi-line callouts no longer silently fall through, hyphenated type names like [!llm-response] now parse, Obsidian's foldable [!type]- syntax is supported, and the pipeline doc codifies the policy that callout bodies must support every LFM feature — directives, citations, embeds, even nested callouts.