refactor: extract outputFormatter collaborator from eventLoop

The printCb and warningCb function fields on eventLoop bundled two
distinct concerns (pair emission and warning delivery) directly on the
event-processing struct. This commit extracts them into a dedicated
outputFormatter type that owns these callbacks plus emit() and
notifyWarning() helper methods.

outputFormatter is embedded (not pointed-to) in eventLoop so that
existing call sites — including tests that write el.printCb = ... and
el.warningCb = ... directly — require no changes beyond the three
struct-literal sites in eventloop_filter_test.go that used field
initialiser syntax.

fdTracker and commResolver were already proper collaborator types; only
the output concern needed extraction.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions