[AZ-446] CSV reporter: band + ci95 annotations + report.csv emitter

Batch 89 — adds optional `band`, `ci95_low`, `ci95_high` kw-only
parameters to `_NfrRecorder.record_metric` and emits a new per-metric
report.csv artifact (one row per scenario × metric, columns:
scenario_id, metric_name, value, value_band, ci95_low, ci95_high,
ac_id, outcome). Backwards compatible — existing 4-arg callers
unchanged; unbalanced ci95 pair raises ValueError. report.csv is
written once per pytest session from `pytest_sessionfinish` so the
annotation pass runs once per CI invocation regardless of
(fc_adapter, vio_strategy) (AC-3). `regression-baseline.json`
intentionally kept flat to preserve the diff contract used by
regression-detection tooling.

NFT-RES-03 + NFT-PERF-01 scenarios updated to pass real bands and
compute empirical 2.5/97.5-percentile ci95 from their own sample
streams (per-iteration envelope ratios for Monte Carlo,
per-frame latency samples for N-sample latency).

Tests: 1229 e2e/_unit_tests pass (+6 vs. batch 88 for AZ-446
band/CI behavior, value-error on unbalanced ci95, report.csv columns,
explicit-path override, and end-to-end emission via the pytest
plugin). Code review: PASS_WITH_WARNINGS — 1 Low (empirical-CI
semantics, documented inline), 1 Medium carried over from batch 88's
cumulative-review backlog (write_csv_evidence + _resolve_fixture_path
duplication is outside AZ-446 reporting scope).

This commit closes Step 10 Implement Tests for cycle 1 (41 of 41
blackbox-test tasks done, AZ-406..AZ-446). Greenfield auto-chains to
Step 11 Run Tests next.

Co-authored-by: Cursor <cursoragent@cursor.com>

_docs/03_implementation/batch_89_cycle1_report.md

@@ -0,0 +1,58 @@
+# Batch Report
+
+**Batch**: 89
+**Tasks**: AZ-446 (CSV reporter refinements — trend-line + acceptance-band annotations + Monte Carlo CI)
+**Date**: 2026-05-17
+**Cycle**: 1
+**Complexity**: 2 points
+
+## Task Results
+
+| Task | Status | Files Modified | Tests | AC Coverage | Issues |
+|------|--------|----------------|-------|-------------|--------|
+| AZ-446_csv_reporter_refinements | Done | 1 source (nfr_recorder), 2 scenarios (nft_res_03 + nft_perf_01), 1 unit test (test_nfr_recorder) | pass | 3/3 | F1 Low (CI naming semantics, in-scope), F2 Medium (carry-over from batch 88, not in scope) |
+
+## AC Test Coverage: All covered (3 of 3 ACs)
+
+## Code Review Verdict: PASS_WITH_WARNINGS
+
+See `_docs/03_implementation/reviews/batch_89_review.md`. 0 Critical / 0 High / 1 Medium (cumulative-review carry-over from batches 85–88: `write_csv_evidence` + `_resolve_fixture_path` duplication is outside AZ-446 scope — surfaces again at the next cumulative review) / 1 Low (empirical-CI naming semantics, documented in nfr_recorder docstring).
+
+## Auto-Fix Attempts: 0
+
+## Stuck Agents: None
+
+## Test Results
+
+- `e2e/_unit_tests/reporting/test_nfr_recorder.py` — 14 tests pass (8 pre-existing + 6 new for AZ-446 band/CI behavior).
+- Full e2e unit-test suite: **1229 passed in 134 s** (+6 vs. batch 88).
+- No scenario-level regressions: NFT-RES-03 + NFT-PERF-01 scenarios continue to skip cleanly via `sitl_replay_ready` / `tier2_only` gating in the Tier-1 docker harness.
+
+## API Change Summary
+
+`_NfrRecorder.record_metric` (and the underlying `_RunAggregator`):
+
+```python
+record_metric(
+    name, value, ac_id=None, *,
+    band: str | None = None,
+    ci95_low: float | None = None,
+    ci95_high: float | None = None,
+)
+```
+
+- All new params kw-only, default `None` — fully backwards compatible.
+- Unbalanced `ci95_*` → `ValueError`.
+
+New artifact:
+
+- `<evidence_dir>/report.csv` (one row per (scenario, metric)) —
+  columns: `scenario_id, metric_name, value, value_band, ci95_low,
+  ci95_high, ac_id, outcome`. Emitted once per pytest session by
+  `_PluginHooks.pytest_sessionfinish` (AC-3).
+
+`regression-baseline.json` schema is unchanged (flat `{metric:
+numeric}`) to preserve the diff contract used by regression-detection
+tooling.
+
+## Next Batch: None — all selected test-implementation tasks are done (Step 10 Implement Tests complete for cycle 1).