Address review feedback on PR #1738:
- ReactLoopAgent builds its AgentEventDispatch once in the constructor and
routes every emit/serial/waterfall through it, so hot-path dispatches no
longer allocate a carrier and dispatcher per call; the public carrier
field is gone (fused dispatcher is private).
- agentEvents accepts an optional prebuilt carrier.
- The fused payload builder spreads the payload before the injected agent
so a structurally acceptable payload carrying an agent field can never
override the subject.
- Regenerate doc graphs; re-record core + architecture + affected Agent
Note translation pairs; add payload-object event contract Agent Note.
The public classifier existed to defend an exported reader against
arbitrary signals, but its only production caller is the loop reading
its own machine-private turn signal, where cancel() is the sole aborter
and always writes one frozen canonical cause. Delete the export and its
15-line structural validation: settle() states the slot invariant with
one cast, the boolean call sites ask signal.aborted directly, and the
retry veto drops entirely because a requested window already implies a
live signal (cancel() retires the window before aborting).
The abort(reason) channel and first-wins semantics are unchanged; only
the reader's publicness is gone, and with it the paranoia it required.
