Event-driven I/O dispatch

Foundation capability (taktora-executor v0.1): inter-process inputs and outputs flow through iceoryx2 channels so producers wake consumers without polling.

Feature: Event-driven I/O dispatch FEAT_0012
status: open
satisfies: FEAT_0010
is satisfied by: REQ_0010, REQ_0011, REQ_0012, REQ_0013
is implemented by: BB_0026

Inter-process inputs and outputs flow through iceoryx2 channels so producers wake consumers without polling.
Requirement: Subscriber-triggered ingestion REQ_0010
status: implemented
satisfies: FEAT_0012
is verified by: TEST_0107
links outgoing: BB_0026, TEST_0107

The runtime shall trigger an item’s execute whenever a declared Subscriber<T> receives a new sample.
Requirement: Publisher-driven emission REQ_0011
status: implemented
satisfies: FEAT_0012
is verified by: TEST_0108
links outgoing: BB_0026, TEST_0108

The runtime shall expose Publisher<T> send paths (send_copy, loan_send, loan) for emitting outputs to other processes.
Requirement: Zero-copy IPC transport REQ_0012
status: implemented
satisfies: FEAT_0012
is verified by: TEST_0109
links outgoing: BB_0026, TEST_0109

Pub/sub data transfer between processes shall be zero-copy across shared memory via iceoryx2; receivers shall obtain a borrowed view of the producer’s payload, not a deserialised copy.
Requirement: Notification-drop visibility REQ_0013
status: implemented
satisfies: FEAT_0012
is verified by: TEST_0113
links outgoing: BB_0026, TEST_0113

The runtime shall surface dropped event-service notifications to the sender as a non-error counter (NotifyOutcome::listeners_notified) so the sender can detect consumer back-pressure programmatically.