Merge R2-06 ServerHistorian fail-fast + 0.2.0 DataType (arch-review round 2) [PR #427]

Findings 06/S-11 (fail-fast ServerHistorianOptionsValidator, no UriFormatException
crash-loop), 06/U-7 (0.2.0 Boolean->Int1 explicit-presence + retype probe),
06/C-7 (keep-populating decision doc). T12 live VPN gate deferred. STATUS.md conflict
(R2-12 bookkeeping) resolved additively. Build clean.

archreview/plans/STATUS.md

@@ -164,3 +164,9 @@ clean. **OPEN follow-ups:** (a) when a runner-reachable fleet + a real `tests/Se
 add a fresh E2E workflow WITH a zero-match guard (fail if `Category=E2E` matches nothing); (b) S-2
 option #2 — a fixture-backed integration leg (opc-plc `services:` block, `MIN_EXECUTED=1`) covering
 what the unit leg cannot; (c) migrate the 3 xunit v2 holdouts once Akka ships an xunit.v3 TestKit.
+
+### Round-2 remediation landed
+
+| Plan | Findings | Branch | Commits | Status |
+|---|---|---|---|---|
+| **R2-06** | 06/S-11 (rank 7), 06/U-7 (rank 8), 06/C-7 | `r2/06-serverhistorian-failfast` (off `1676c8f4`) | `3a049a13`…`4640ecb1` (10 task commits) | **Code-complete, offline-verified.** S-11: fail-fast `ServerHistorianOptionsValidator` (consumer-gated on `ServerHistorian:Enabled` OR `AlarmHistorian:Enabled`, fails empty/non-http(s) Endpoint at startup) + `AddValidatedOptions` wiring + adapter defense-in-depth (`TryCreate`→named `InvalidOperationException`, no more raw `UriFormatException` crash-loop) + `Validate()` warning parity + alarm-only-mode startup warning. U-7: pinned Boolean→Int1 explicit-presence (`HasDataType`) + `HISTGW_BOOL_SANDBOX_TAG` live Boolean EnsureTags leg + retype probe (skip-clean offline) + upsert/retype migration note (`docs/Historian.md`). C-7: keep-populating decision + dead-`Quality` doc comments (0.2.0 C-002). **Live leg operator-gated (T12) — pending a VPN run on a 0.2.0 gateway** (records the observed in-place retype policy back into `docs/Historian.md`; also discharges 06/U-2's full documented run). |