feat: add historical account FX lifecycle

[luisleo526]

What

• add an append-only C ABI for effective-time quote-to-account FX curves
• route historical sizing, admission, open P&L, commissions, realized P&L, and the TV-pinned 1x carried-long broker rollover through the active FX value
• freeze signal-time FX and entry-time commission snapshots at their actual lifecycle boundaries
• add the JSON daily-close adapter and fingerprint the exact effective values plus raw provider provenance
• fail closed for unsupported streaming/COOF/magnifier routes, carried short/leveraged rate changes, and any failed public-corpus execution
• document the 27-symbol ABI and historical-run support boundary

Why

The previous scalar account_currency_fx setting applied one present-day value to an entire historical run. That retroactively repriced position notional, P&L, and fees, and it also mixed signal-time sizing with fill-time conversion. A second masking defect recomputed already-paid open-entry commission at the new rate during an FX rollover. Together those lifecycle errors could hide or manufacture broker margin actions.

The new curve is inclusive as-of with scalar fallback before its first point. Daily provider closes become effective at D+1 00:00 UTC in the harness. Entry fees remain fixed at their fill-time account value while TradingView-compatible realized trade reporting continues to convert the complete trade at exit-time FX.

Verification

• ctest --test-dir build --output-on-failure -j 16: 113/113 passed
• python3 scripts/fingerprint_self_test.py: 78/78 passed
• python3 scripts/run_corpus_self_test.py: 5/5 fail-closed cases passed
• JOBS=16 scripts/run_corpus.sh: 252/252 strategy executions passed; 247 Excellent / 4 Strong / 1 known anomaly
• canonical 416-strategy downstream gate: 355 Excellent / 46 Strong / 4 Moderate / 2 Weak, +1 upgrade / 0 downgrades; expected error identities unchanged
• exhaustive N=5 interaction matrix: 32/32 cells passed, GO; all-off consumer Strong, all-on Excellent at 100% and count delta 0; direct production tapes match the all-on cell exactly
• final production identity rerun matched both graded consumers across all 12 semantic/tape fields (domain-result.json SHA-256 5f85f1491efe1969055c94d09eb9db3432b2b6f021f78e76266ddfb865ac089a)
• injected runner-failure smoke: error surfaced and run_corpus.sh exited before stale-output verification
• bash -n scripts/run_corpus.sh and git diff --check