Issue #1836: Restore lost Issue #1081 regression suite (append-only)

Problem statement

Commit 797396d9d (fix(#1691)) performed a full-file rewrite of tmp/TLU_Test_Cases.md (+0/-128 diff vs f42e37830) instead of appending the new #1691 suite. This destroyed the ## Task — Issue #1081: generated-on timestamp footer in searchReqSpec regression suite. Total heading count remained unchanged (85→85), so count-based checks did not detect the loss (documented class in ai/AGENTS.md rule 9; matches prior cases #1701, #1740, #1048).

Root cause

• Agent regenerated the entire suite file from a stale snapshot (missing content added after that snapshot), violating append-only rule for the shared tmp/TLU_Test_Cases.md.
• Detection gap: count-based checks are blind to set substitution; gate must compare set of ^## headings against merge-base.

Fix

• Restored the lost #1081 suite by appending its exact text verbatim from f42e37830 (heading ## Task — Issue #1081: generated-on timestamp footer in searchReqSpec) to tmp/TLU_Test_Cases.md (no rewrite).
• Added new regression suite ## Regression — Issue #1836: restore lost Issue #1081 regression suite (append-only) (append-only).
• Verified with ai/verify_test_suites.sh using merge-base comparison (7 PASS / 0 FAIL).

Verification (measured)

• git show f42e37830:tmp/TLU_Test_Cases.md | grep -c 'Issue #1081' >= 1 (original)
• grep -c 'Issue #1081' tmp/TLU_Test_Cases.md = 2 (restored + present)
• TLU_REQUIRE_SUITE="Issue #1081" bash ai/verify_test_suites.sh → 7 PASS / 0 FAIL / 0 SKIP
• TLU_REQUIRE_SUITE="Issue #1836" bash ai/verify_test_suites.sh → 7 PASS / 0 FAIL / 0 SKIP
• No suites lost vs merge-base; no lines removed; fences balanced; no heading without body.

Files changed

• tmp/TLU_Test_Cases.md (appended two suite blocks; git-ignored but content restored)

Commits

• 9f96bd573 fix(#1836): restore lost Issue #1081 regression suite (append-only), add Issue #1836 regression suite (Refs #1836)

Conclusion

Data-loss defect in suite file fixed by strict append-only restoration from history; gate passes. Issue closed with verification.