Mark jumps into other functions as tail calls

We can mark them with an argument, as well as a flow marker (arrow from one frame to the other).

We may need to special-case this for OCaml-only, depending on how this interacts with other languages.

No file or test is named. Start by tracing how magic-trace represents jumps between frames and how language-specific handling is selected; define the argument and flow marker for jumps into other functions, then verify whether OCaml-only special-casing is required.

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