feat(math): participant-ban leak replication in clojure-legacy mode (Q1)

[jucor]

The Clojure math worker NEVER honored participants.mod = -1: its ingest path
has no mod filter, so banned participants keep influencing user-vote-counts,
in-conv, PCA, clustering and repness. Python's real ban feature
(mod_out_ptpts row drop in _apply_moderation, 2026-06-10) is correct but a
certification divergence.

clojure-legacy mode now stores mod_out_ptpts without applying it (rows kept;
single choke point: the _apply_moderation row drop is gated on improved
mode). Everything downstream then leaks exactly like Clojure. improved mode
keeps the ban byte-for-byte.

Supersedes the legacy-mode premise of #2623's T1 carry-prune test: banning
can no longer shrink the legacy clustering pool, so the stale-carry trap
cannot arise; the vote_counts intersection stays as belt-and-braces
(comment updated) and the test now pins ban-invariance
(TestCarryUnderParticipantBan).

TDD: tests/test_mod_ptpt_leak_parity.py — 4 legacy tests RED on old code
(rows dropped / not clustered / not counted / not in-conv), GREEN after;
improved-mode pin green throughout. Neighbors green: greedy-carry +
degenerate-tick suites (22 passed), discrepancy moderation subset
(19 passed, 6 pre-existing data skips).

commit-id:d4116474

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Stack:

• ci: run postgres integration tests #2637
• feat(math): moderation + restart-seam replay coverage — mod_update parity, Q13-Q16 #2656
• docs(delphi): R1-parity goal docs, journal (2026-07-18 → 07-22 s3), quirks + divergence ledger #2626
• feat(delphi): Q12 carve-out — pin the cold-tick PCA start to ones in both replay drivers #2655
• feat(math): Q11 — replicate vectorz distance cancellation in legacy kmeans #2654
• feat(math): small-N degenerate parity — run the real math on tiny matrices in clojure-legacy mode #2653
• feat(delphi): Q10 carve-out — pin large-conv cutoffs to certify the deterministic full-PCA path #2652
• feat(delphi): replay loader resolves private datasets under real_data/.local #2651
• feat(math): Clojure hash-map iteration order for the in-conv greedy tie-break (legacy) #2650
• feat(math): clojure-legacy blob emission + selection parity — Clojure-exact math_main at step 0 #2649
• feat(delphi): acceptance canonicalization — suppress cross-engine ordering artifacts in certify comparer #2648
• feat(delphi): certify.py battery runner + focuser + fingerprint ledger (Spec A, Phase 0) #2647
• feat(delphi): prodclone extractor — feature-filtered dataset export (Spec B) #2646
• feat(math): un-mirror priority_metric (#2571 resolved) + Q2 prev-tick group-votes #2645
• feat(math): participant-ban leak replication in clojure-legacy mode (Q1) #2644 ⬅
• feat(delphi): Clojure timing probe (Spec C) #2643
• feat(math): degenerate-tick group-clusterings overwrite + <2-participants edge (legacy mode) #2642
• refactor(math): move impl-flag resolver to polismath/utils/env_flags.py #2641
• feat(delphi): Python math poller service (phase 1) — Clojure math-container replacement #2625
• fix(delphi): Clojure-parity math writers + committing write path in PostgresClient #2624
• feat(math): in-conv greedy floor + persistent carry (PR-E) #2623
• feat(math): Clojure-exact base-cluster lineage + warm start (PR-C) #2622
• feat(math): replay harness H-B — Clojure Mode A driver (dev/replay.clj) + cross-language comparer shim #2621
• feat(math): group-k-smoother in clojure-legacy engine mode (PR-D smoother) #2620
• feat(math): PCA warm start in clojure-legacy engine mode (PR-B) #2640
• feat(math): add POLISMATH_ENGINE_MODE flag + prev-tick warm-start scaffolding (PR-A) #2618
• feat(delphi): replay harness H-A — schedule spec+slicer, Python driver, store, step comparer, CLI #2639
• fix(delphi): cold-start generator copies FULL revote history (no DISTINCT ON dedup) #2638
• fix(math): correct comment-extremity sign in pca_project_cmnts (D1b) #2615
• docs(delphi): add math-algorithm history & routing-regression reference #2613

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⚠️ Part of a stack created by spr. Do not merge manually using the UI - doing so may have unexpected results.