Restructure docs: per-device directories under modules/ and nics/ with co-located datasheets, state centralized in state.md, prose tightened into lists and tables

docs/modules/fibergaga/README.md

@@ -0,0 +1,21 @@
+# Fibergaga SFP-10G-T-30M (Aquantia AQR)
+
+The documented oracle. RollBall module, PHY ID 0x31c31c13, proven over the i40e oracle path ([../../nics/x710/](../../nics/x710/README.md)). Its PHY family register reference is vendored in this directory (`aquantia-aqr107-aqr109-datasheet.pdf` — the AQR107-AQR109 register reference).
+
+## Documented registers
+
+| Registers | What |
+|---|---|
+| 3.E820/3.E821 | PCS Receive Vendor **Uncorrected** Frame Counter (post-FEC) |
+| 3.E840–3.E84E | Corrected Frame N Iteration Counters, N = 1…10 LDPC iterations — the pre-FEC leading indicator ([../../open-questions.md](../../open-questions.md) §5) |
+| 3.E816 | RS Corrected Error Frame Counter (system-side, secondary) |
+| 1E.C884 bits 7:0 | **Estimated cable length in meters, ±1 m**, RO, from the cable diagnostic engine |
+| 1E.C800 | Per-pair TDR fault verdicts (open/short/mismatch/cross-pair) |
+| 1E.C801–C807 | Distances of the four worst reflections per pair, ±1 m |
+| 1E.C880–C883 | Reflection impedance/magnitude |
+| PMA 1.133–1.140, PCS 3.32/3.33 | Standard set ([../README.md](../README.md)), proven live |
+
+## Open bench questions
+
+- Whether `1E.C884` is continuously valid on a linked cable or only after an explicit diag run.
+- The pre-FEC correlation experiment ([../../open-questions.md](../../open-questions.md) §5) — this module is its instrument.