Relative links in Markdown point at files that exist

Every relative link and image in a Markdown file resolves to a real file in the repository.

Why it is a rule

Documentation is the part of a change nothing type checks. Move or rename a source file and every import either updates or the build fails; a README that pointed at the old path keeps pointing at nothing, and the first person to notice is a reader months later. Automated refactors are especially prone to this, because they update every reference the compiler checks, and Markdown is not one of them.

What is expected

Relative targets (./docs/guide.md, ../README.md, images/flow.png) exist at the resolved path. A leading / resolves from the repository root. Anchors and queries are ignored: guide.md#setup checks only that guide.md exists.

External URLs, mailto: links and pure #anchor links are not checked; this rule only covers what a commit in this repository can break. Link syntax inside fenced code blocks and inline code spans is treated as example text and skipped.

Exceptions

A link that must point at a generated or git-ignored file (one that exists after a build but not in a fresh checkout) is better rewritten to point at the source that generates it. If that is not possible, exclude the document via the rule's exclude globs.