Parses .http / .rest request files — the format shared by the VS Code
REST Client extension and the JetBrains HTTP Client.
Requests are separated by ###; the text after ### is a name/comment.
A request is METHOD url [HTTP/version] (the method is optional and
defaults to GET), followed by header lines, a blank line, and an
optional body. {{var}} placeholders resolve from in-file @name = value
definitions; anything left unresolved in the path is treated as a path
parameter (:var) rather than literal text. JetBrains response-handler
blocks (> {% ... %} / > script.js) are skipped.