Function lintFlows

Statically check a bot's flows (or a plain list of flows) and return structured diagnostics, most severe first (stable within a severity).

Opaque code is never guessed at: async conversations, .do()/then actions, dynamic texts and predicate triggers are treated as "could do anything" — including c.goto() to any flow — so the linter only warns about what is certain from the declared structure. See LintCode for every check.