OTP application callback for Exgit.
Starts a minimal supervision tree that only exists to support opt-in process-based features:
Exgit.TaskSupervisor—Task.Supervisorused byExgit.FS.prefetch_async/2to run background prefetches under supervision. The supervisor usesrestart: :temporarysemantics by default (Task.Supervisor never restarts a dead task), so a crashed prefetch is logged and forgotten, not infinitely retried.
Callers who use only the pure-value API (Exgit.clone/2,
Exgit.FS.grep/4, etc.) pay for this supervisor but its cost
is negligible: one idle Erlang process (<1 KB). If even that is
unacceptable, build with otp_app: false — but then
Exgit.RepoHandle, Exgit.FS.prefetch_async/2, and
Exgit.RepoRegistry will not be available.
The Exgit.IndexCache ETS owner is also started here for the
pre-existing idx view cache.