Snapshot PINK DITAv2 system + Sprint 0 flaw-fix verification

First commit of the previously-untracked PINK-on-DITAv2 migration system
(execution moves to the Rust kernel; policy stays on legacy DITA, so Alpha
Engine algorithmic integrity is preserved). BLUE is untouched.

Sprint 0 (safety snapshot + flaw-fix verification, MARKET single-leg scope):
- Verified Rust FSM fixes (flaws 2,4,10,11,13) by source read of lib.rs.
- Hardened 5 vacuous/guarded assertions in test_flaws.py so each flaw test
  genuinely exercises its fix. Most important: Flaw 5 now asserts capital
  moves by EXACTLY realized PnL (was entering/exiting at the same price).
- Offline suites: 533 passed, 0 failed (35 flaws + 402 kernel/accounting/
  bridge + 96 runtime/persistence/multi-exit/restart/seams).
- GATE PASS: MARKET-path-critical flaws 1,2,5 confirmed fixed + green.
- Added SPRINT0_FLAW_VERIFICATION.md report and _rust_kernel/.gitignore
  (excludes Rust target/ build artifacts).

LIMIT/partial-fill remain explicitly out of scope (MARKET-only bring-up).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

prod/clean_arch/dita_v2/venue.py

@@ -0,0 +1,37 @@
+"""Venue adapter contracts for DITAv2."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from datetime import datetime
+from typing import Any, Dict, List, Optional, Protocol
+
+from .contracts import (
+    KernelCommandType,
+    KernelIntent,
+    KernelEventKind,
+    TradeSide,
+    VenueEvent,
+    VenueEventStatus,
+    VenueOrder,
+    VenueOrderStatus,
+)
+
+
+class VenueAdapter(Protocol):
+    """Abstract venue adapter used by the kernel."""
+
+    def submit(self, intent: KernelIntent) -> List[VenueEvent]:
+        ...
+
+    def cancel(self, order: VenueOrder, *, reason: str = "") -> List[VenueEvent]:
+        ...
+
+    def open_orders(self) -> List[VenueOrder]:
+        ...
+
+    def open_positions(self) -> List[Dict[str, Any]]:
+        ...
+
+    def reconcile(self) -> List[VenueEvent]:
+        ...