fix: isolate rejection observer failures

[vycdev2]

Summary

• keep successful mapFulfilled results when an optional rejection observer itself throws
• prevent secondary logging/reporting failures from rejecting the aggregate operation
• add behavioral regression coverage and document the fix

TDD evidence

• Untouched-base RED: TS_NODE_TRANSPILE_ONLY=1 npm test -- --grep "rejection handler throws" failed because Error: logging failed escaped from the observer and rejected the whole batch.
• GREEN: the same focused command passed after isolating observer failures.

Verification

• TS_NODE_TRANSPILE_ONLY=1 npm test — passed, 135 tests
• npm run compile — passed
• npm run format:check — passed
• git diff --check upstream/develop...HEAD — passed

Risk

Low. Mapper failures were already intentionally omitted; this only prevents the optional rejection observer from changing that aggregate contract. Successful result ordering is unchanged.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.