#000037 Phase 0: §12 trigger probe + Phase 1 test scaffolding

Phase 0 of ticket #000037 (Prometheus-Σ recursive falsification
controller) is doc-only and gates Phase 1 on §12 measured-pressure
triggers. This commit lands the empirical-evidence harness fox needs
for the go/no-go decision, plus the §16.2 test scaffolding so the
contract is discoverable from the test runner today.

bench/prometheus_sigma_trigger_probe.py
=======================================

Read-only walk of audit_events + capital_ledger across shards.
Reports each §12 trigger:

- Trigger 1 (branch density, ≥4 branches/checkpoint): looks for a
  fork_score branch-set table; reports "no data — single-validator
  ForkScore Phase 1a" when absent. Trigger structurally cannot fire
  until #000012 multi-branch persistence lands.
- Trigger 2 (divergence variance, N≥30 + ratio>0.5 OR abs>0.10):
  aggregates providence_canonical_witness audit-event bodies,
  maps each agreement_label per #000028 §1.2 to a binary
  LLM-divergence score, computes mean/stddev/ratio. Defensive on
  the max(mean,ε) guard from §12 itself.
- Trigger 3 (witness cost share > 0.30): aggregates capital_ledger
  rows; uses `material` (kWh proxy) as the canonical compute axis;
  surfaces both `material` and `financial` so fox can pick a
  different form if needed. Tags the report with the caveat that
  the current ledger reflects ad-hoc activity, not a controlled
  #000026 sweep.
- Trigger 4 (operator mission need): n/a — operator decision.

Pure measurement, no LLM, no schema change, no mutation. Output is
a markdown report at $(PROMETHEUS_PROBE_OUT) (default
bench/results/prometheus-sigma-triggers-<utc-date>.md).

Wired via `make prometheus-trigger-probe`.

bench/results/prometheus-sigma-triggers-2026-05-10.md
=====================================================

First captured baseline. Verdict on current shards:

  Trigger 1: NO  (no fork_score branch-set table; #000012 Phase 1a
                  is single-validator)
  Trigger 2: NO  (16 samples; N_min=30. But mean=0.625, σ=0.5,
                  ratio=0.8 — both ratio AND abs floors would fire
                  if N reaches 30. Signal is there; just needs more
                  samples.)
  Trigger 3: NO  (witness/total material = 0.005, well under 0.30
                  threshold. Caveated: ledger is ad-hoc, not a
                  controlled #000026 sweep.)
  Trigger 4: n/a (operator-stated)

Empirical answer: no §12 measured-pressure trigger has fired yet.
Phase 1 of #000037 remains paper-only unless fox invokes Trigger 4.

tests/test_prometheus_sigma.py
==============================

17 skip-stubs pinning the §16.2 acceptance contract. Each test:

- Collects today via `pytest --collect-only` so the test surface is
  discoverable.
- Skips with reason "Phase 1 not landed; controller module
  arborist/v9/prometheus.py absent" until that import succeeds.
- Carries a one-sentence intent line tying it back to a numbered
  ticket section (§5 / §6 / §7 / §10 / §13 / §14 / §16.1 / §4.4).

When Phase 1 lands, the implementer adds the controller module
under arborist/v9/prometheus.py per §13; CONTROLLER_AVAILABLE
becomes True; each test gets its body filled in. The names, intents,
and skip-reason strings are the durable contract.

Hygiene
=======

- make test → 1623 passed, 45 skipped (was 28; +17 new skips).
- make chain-check-shards → 0 breaks across all 7 shards.
- No code touched outside the new probe + scaffolding files +
  Makefile target wiring. fox's in-flight #000037 ticket
  modifications left untouched.

Makefile

@@ -33,6 +33,7 @@ SEARCH_Q     ?= computer
         chain-check chain-check-shards \
         falsify burn burn-kindergarten inspect bootstrap-crawler test-crawler crawl-ingest \
         recrawl-check bench-qa bench-qa-smoke bench-qa-progressive-and \
+        prometheus-trigger-probe \
         bootstrap-math clean clean-db clean-data help \
         textbooks-summary textbooks-urls fetch-textbooks textbooks-stats textbooks-verify \
         crawl-textbooks crawl-textbooks-stats textbook textbook-list
@@ -229,6 +230,16 @@ test-live: bootstrap ## live QA quality tests against Hermes (gated; -n auto par
 	ARBORIST_LIVE_TESTS=1 ARBORIST_LIVE_SHARDS_DIR=$(SHARDS_DIR) \
 	    .venv/bin/pytest tests/test_qa_quality_live.py -v -n auto
 
+# Prometheus-Σ §12 trigger probe (ticket #000037 Phase 0). Read-only
+# walk of audit_events + capital_ledger across shards; reports
+# whether any of triggers 1-3 have fired empirically. Output is the
+# evidence fox uses to decide go/no-go on Phase 1. Pure measurement.
+PROMETHEUS_PROBE_OUT ?= bench/results/prometheus-sigma-triggers-$(shell date -u +%Y-%m-%d).md
+prometheus-trigger-probe: bootstrap ## #000037 §12 measured-pressure probe → markdown report
+	PYTHONUNBUFFERED=1 $(PY) bench/prometheus_sigma_trigger_probe.py \
+	    --shards-dir $(SHARDS_DIR) \
+	    --out $(PROMETHEUS_PROBE_OUT)
+
 # Concept-layer backfill targets. Each runs an extractor across every
 # wiki shard; per-shard work is independent so we use GNU-parallel-
 # style concurrency with `xargs -P` to overlap the slow paths