Fail closed on unhealthy PnL persistence

[Mopati123]

Summary

• Treat corrupt/truncated PnL state as unsafe instead of silently resetting to zero.
• Mark PnL persistence unhealthy, trigger the risk-manager kill switch, and refuse trade recording while state is untrusted.
• Write PnL state and daily summaries atomically with temp file, fsync, and replace.
• Surface persistence health in daily stats.

Validation

• python -m pytest tests/rootfile/test_pnl_persistence_safety.py -q -> 4 passed
• python -m pytest tests/rootfile -q -> 119 passed
• git diff --cached --check -> passed

Safety

• No broker execution or canary run in this pass.
• .github, .env, logs/, data/, and runtime artifacts were not included.
• kluster was attempted after edits, but review is blocked because the trial has ended.