docs(adr): ADR-084 — promote Proposed → Accepted

All five implementation passes plus four security-review hardenings
shipped in PR #435 (squash-merged as d71ef9a). Acceptance numbers
measured on synthetic AETHER-shape data:

- Compare-cost reduction: 8x-30x floor → 43-51x pair-wise (d=512),
  12.4x top-K (d=128 n=1024 k=8), 7.6x full pipeline (d=128 n=4096 k=8).
- Top-K coverage: ≥90% floor → 90%+ at prefilter_factor=8 (78.9%
  at factor=4 documented as fail; codified in
  test_search_prefilter_topk_coverage_meets_adr_084).
- Wire envelope: 28-byte AETHER 128-d (vs 512-byte raw float; 18x
  compression).

The third acceptance criterion (`< 1 pp end-to-end accuracy regression`)
needs a real-CSI soak test against a multi-day AETHER trace; that's
post-merge follow-up rather than a merge-blocker. Synthetic-data
acceptance was sufficient evidence to ship.

PR #434 (ADR-086 firmware-side gate) merged separately as 17509a2.

Co-Authored-By: claude-flow <ruv@ruv.net>

docs/adr/ADR-084-rabitq-similarity-sensor.md

@@ -2,7 +2,7 @@
 
 | Field          | Value                                                                                   |
 |----------------|-----------------------------------------------------------------------------------------|
-| **Status**     | Proposed                                                                                |
+| **Status**     | Accepted — Passes 1–5 + L1–L4 hardening implemented and merged via PR #435 (commit `d71ef9a`); acceptance numbers in §"Acceptance test" all measured and passing on synthetic AETHER-shape data; the `< 1 pp end-to-end accuracy regression` criterion is tracked as a post-merge soak test |
 | **Date**       | 2026-04-26                                                                              |
 | **Authors**    | ruv                                                                                     |
 | **Refines**    | ADR-024 (AETHER re-ID embeddings), ADR-027 (cross-environment domain generalization), ADR-076 (CSI spectrogram embeddings), ADR-081 (5-layer firmware kernel) |