Outgoing links and citations

sheriff validate resolves the target of every outgoing link among the sids that exist. It reads the citations in every node and sets them against the links the node makes:

• A § followed by a sid and then by no lower-case letter or digit cites that sid.
• A § followed by anything else, up to a space, a comma, a semicolon or a closing parenthesis, is a citation by a location.
• Text in backticks counts in the check as any other text does, except a citation by a location (§s-bpdqd9v72wg7vsz).
• A header's index and the values gathered beside a field are not read.