refactor(bayn): check every production index access

[gregkonush]

Summary

• adds a production-only TSGo profile with noUncheckedIndexedAccess while retaining the full profile for tests and fixtures
• replaces unchecked production indexing with explicit fail-closed domain results across market data, reconciliation, execution, persistence, and forward-performance paths
• adds typed missing-reference failures instead of allowing implicit undefined to cross domain boundaries

Related Issues

None

Testing

• bun run --filter @proompteng/bayn tsc
• bun run --filter @proompteng/bayn lint
• bun run --filter @proompteng/bayn lint:oxlint:type
• bun run --filter @proompteng/bayn test (1,054 pass, 160 environment-gated skips, 0 fail)
• bun run --filter @proompteng/bayn build (793 modules)

Breaking Changes

None

Checklist

• Testing section documents the exact validation performed (or N/A with justification).
• Screenshots and Breaking Changes sections are handled appropriately (removed or filled in).
• Documentation, release notes, and follow-ups are updated or tracked.

[gregkonush]