fix: preserve LFTJ admission errors and cleanup (#1369)

[justinjoy]

Summary

• Preserve ENOSPC, EOVERFLOW, EINVAL, and ENOMEM distinctions in governed LFTJ execution.
• Release temporary workspace reservations when iterator allocation fails.
• Propagate inner governor denial to the session and test denial, cleanup, and retry.
• Document remaining Enforce memory admission at every allocation class; replace the join row cap and deprecate WIRELOG_JOIN_OUTPUT_LIMIT #1369/Clarify and enforce memory admission for operator temporaries #1978 allocation boundaries.

This is a partial #1369 fix and does not close #1369.

Validation

Validated after rebasing onto current main at 74194e26e73be786d8094fe7027f6dda2bea05bd:

• meson test -C build lftj lftj_integration memory_admission_join --print-errorlogs — all three tests passed.
• uncrustify -c uncrustify.cfg --check wirelog/columnar/lftj.c wirelog/columnar/lftj.h wirelog/columnar/ops.c tests/test_lftj.c tests/test_lftj_integration.c — passed.
• scripts/ci/check-threading-doc.sh — passed; all 222 atomic-site audit rows covered.
• git diff --check origin/main...HEAD — passed.

Hosted CI for this rebased head is running.