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/utils.py

@@ -0,0 +1,43 @@
+"""Utility helpers for the DITAv2 kernel."""
+
+from __future__ import annotations
+
+from dataclasses import asdict, is_dataclass
+from datetime import datetime
+from enum import Enum
+from typing import Any
+import json
+import math
+
+
+def safe_float(value: Any, default: float = 0.0) -> float:
+    """Return a finite float or ``default``."""
+    try:
+        out = float(value)
+    except Exception:
+        return default
+    if not math.isfinite(out):
+        return default
+    return out
+
+
+def json_safe(value: Any) -> Any:
+    """Convert enums, dataclasses and datetimes to JSON-safe objects."""
+    if isinstance(value, Enum):
+        return value.value
+    if isinstance(value, datetime):
+        return value.isoformat()
+    if is_dataclass(value):
+        return json_safe(asdict(value))
+    if isinstance(value, dict):
+        return {str(key): json_safe(val) for key, val in value.items()}
+    if isinstance(value, list):
+        return [json_safe(item) for item in value]
+    if isinstance(value, tuple):
+        return [json_safe(item) for item in value]
+    return value
+
+
+def json_text(value: Any) -> str:
+    """Serialize a value using stable JSON settings."""
+    return json.dumps(json_safe(value), separators=(",", ":"), ensure_ascii=False, default=str)