Function parseFileDirectives

Parse every <!-- mermaid-lint-disable-file ... --> directive in a Markdown document. Document-level directives carry the real 1-indexed document line the directive keyword starts on (not the line of any particular Mermaid block) — they apply to every block regardless of position.

An HTML comment whose opening <!-- falls inside a fenced code block or an inline code span is skipped entirely — see codeRanges. That is what keeps documentation showing the directive syntax (e.g. this project's own README) from being parsed as a live directive.

A single HTML comment may pack more than one directive (e.g. copy-pasted blocks or several independent suppressions). Each occurrence of any directive keyword starts its own directive; the text between consecutive occurrences (and from the last occurrence to the end of the comment) is that directive's rule list and reason. This avoids silently folding a second directive into the first one's reason string. Keywords other than -disable-file are also scanned for here (not skipped) so a keyword used at the wrong scope — e.g. <!-- mermaid-lint-disable-next-line ... --> — is reported via wrong-scope instead of silently doing nothing.