dita_v2: VenueTelemetrySnapshot + Zinc venue plane (4th shm partition) + local Rust target dir

Upstream-canonical commit of the ~366 lines that sat uncommitted in the working
tree (surveyed in DITAV2_SOA_SURVEY_20260702). Venue telemetry published at every
venue boundary (submit/cancel/reconcile) over the zinc venue_region; SOA per
UV DITAv2 adjudication 2026-07-03.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

prod/clean_arch/dita_v2/__init__.py

@@ -32,6 +32,7 @@ from .contracts import (
     VenueEventStatus,
     VenueOrder,
     VenueOrderStatus,
+    VenueTelemetrySnapshot,
 )
 from .journal import ClickHouseKernelJournal, KernelJournal, MemoryKernelJournal
 from .rust_backend import ExecutionKernel
@@ -89,6 +90,7 @@ __all__ = [
     "VenueEventStatus",
     "VenueOrder",
     "VenueOrderStatus",
+    "VenueTelemetrySnapshot",
     "ZincPlane",
     "ZincControlPlane",
     "build_position_state_row",