macula_feeder callback implementation for hecate_om_content:put/1,2.

Named for the SDK contract it satisfies, not for the caller-facing operation (put) — unlike the facade, this file carries no domain content of its own. Every bit of real logic (mesh handle resolution, realm override, timeout, cancel-on-timeout) lives in hecate_om_content; this module exists purely because macula_feeder needs an init/1/handle_fed/2 pair to call, and the single most salient fact about it is which contract that is.

Split out from hecate_om_content itself (rather than declaring both -behaviour(macula_feeder) and -behaviour(macula_download) on one module) because the two behaviours both declare init/1 — the compiler rejects that combination outright ("conflicting behaviours"), and dropping the attributes to work around it would trade away real callback-arity/missing-callback checking for convenience. Not meant to be called directly by anything but hecate_om_content and macula_feeder itself.