fix: release uniquely owned bracket slots while preserving FIFO history

[luisleo526]

A bracket that fully closed its own uniquely identified lot could leave its pyramid slot occupied, incorrectly rejecting a later entry. The ordinary two-slot FIFO path now releases that slot only after proving the owner lot retired and one distinct lot remains. A lot previously reduced by a foreign or ambiguous bracket keeps its slot history, preserving the existing cross-ID FIFO rejection behavior.

Validated on engine 6b1f4f12f4da40d172b54d41d81c7e8e84ef8d52 with codegen 3fd97fe28abd7b191cb376d9f5db4e056fcfae4b:

• Cloud Run measured all 4,190 probes in 72/72 cases. Thulashimohanr EURUSD moves from strong to excellent: canonical count difference 1 to 0 and match 99.5% to 100%. The other 4,189 canonical results are unchanged, with zero regressions, errors or gaps. Result: 4,161 excellent / 29 strong / zero moderate.
• Gate pineforge-pr-gate-m99r6: PASS, target score +1, and zero regressions or tolerated exceptions across 704 hard probes.
• Fresh build and 212/212 tests passed, including 81 focused checks covering owned retirement, prior foreign FIFO slices, full/partial/zero effects, both directions, and reuse. Covered TradingView controls support the ownership distinction. Independent Grok 4.6 review of this exact candidate is GREEN, P0/P1/P2 = 0.

The target adds exactly the missing November 19 entry and its November 20 exit, with no existing economic rows removed. Existing split-versus-combined row differences in two trades and the final range-end mark remain; this is not a claim of complete economic identity.

Grading metrics, thresholds, tolerances, verifier, harness, tapes and population are unchanged. Existing ambiguous same-ID, cross-owner FIFO, ANY, POOC, COOF, magnifier and streaming paths retain their prior release rules.

Candidate snapshot: 6608bf86d773f16b7120a40488e57ee63c5f922c57c95e602c550e69e50c796b (788,854 bytes).