docs(grpc): matrix + plan reflect ext-prop fix, SQL prime result, ConnStatus

- README transport matrix: GetTagExtendedProperties notes the multi-property parser
  fix; AddTagExtendedProperties read-back now round-trips; GetConnectionStatus gRPC
  -> live-verified; ExecuteSqlCommand notes the RegisterTags prime does not help.
  Refresh the closing production-pattern guidance.
- grpc-tooling-completion.md: mark #5 (ConnStatus) done, #4 (SQL prime) negative, and
  the #1 ext-prop read-back follow-up done.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B6mcaT2PjRFKcogzp9UkfC

README.md

@@ -86,13 +86,13 @@ request rides the RPC but the server faults on an unmet precondition) ·
 | `GetServerTimeZoneAsync` | ❌ | ✅ | 2020 `GetSystemTimeZoneName` is a client-side stub (empty); WCF throws |
 | `GetStoreForwardStatusAsync` | ⚠️ | ✅ | gRPC contacts the server (measured idle-state, reports `ErrorOccurred`); WCF returns synthesized all-false. Active-SF magnitude is D2-gated on both |
 | `GetRuntimeParameterAsync` | ✅ | ✅ | tooled + live-verified over gRPC (`StatusService.GetRuntimeParameter`, the 2020 `GETRP` buffers ride unchanged) |
-| `GetTagExtendedPropertiesAsync` | ✅ | ✅ | tooled + live-verified over gRPC (`RetrievalService.GetTagExtendedPropertiesFromName`, the `GetTepByNm` buffers ride unchanged) |
-| `ExecuteSqlCommandAsync` | ✅ | ⛔ | gRPC request rides `RetrievalService.ExecuteSqlCommand`, but the server-side `CSrvDbConnection.ExecuteSqlCommand` faults (`IndexOutOfRange`, native err 38) — an unmet DB-connection precondition; bounded behind `ProtocolEvidenceMissingException`. Use WCF |
+| `GetTagExtendedPropertiesAsync` | ✅ | ✅ | tooled + live-verified over gRPC (`RetrievalService.GetTagExtendedPropertiesFromName`, the `GetTepByNm` buffers ride unchanged). The shared parser now handles the live multi-property response shape (one group per property + a uint16 searchability-flags trailer), fixed 2026-06-22 |
+| `ExecuteSqlCommandAsync` | ✅ | ⛔ | gRPC request rides `RetrievalService.ExecuteSqlCommand`, but the server-side `CSrvDbConnection.ExecuteSqlCommand` faults (`IndexOutOfRange`, native err 38) — an unmet DB-connection precondition. A `HistoryService.RegisterTags` prime does **not** clear it (tried live 2026-06-22, both 0x402/0x401). Bounded behind `ProtocolEvidenceMissingException`. Use WCF |
 | `ReadEventsAsync` | ✅ | ⚠️ | tooled + routed over gRPC: the full CM_EVENT registration replay (`UpdateClientStatus`→`RegisterTags`→`EnsureTags` + discovery probes) runs and `StartEventQuery` succeeds, but `GetNextEventQueryResultBuffer` **long-polls** on no data (it blocks to the deadline rather than returning the synchronous 5-byte code-85 terminal the WCF op gives). The read is **hard-bounded** (≤30s) and throws `ProtocolEvidenceMissingException` on the no-row path rather than assert a false empty. Row-level retrieval is **not yet live-verified** — the dev box holds no events; pending a capture against an event-bearing 2023 R2 server. Use WCF for event reads |
 | `SendEventAsync` | ✅ | 🔌 | rides `AddStreamValues` family; no distinct event-send RPC, framing uncaptured over gRPC |
 | `EnsureTagAsync` / `DeleteTagAsync` / `RenameTagsAsync` | ✅ | ✅ | live-verified 2026-06-22 over gRPC (`HistoryService.EnsureTags` / `DeleteTags` / `StartJob`, write-enabled 0x401 session, WCF serializers reused) via a self-cleaning sandbox-tag lifecycle. Rename is an async StartJob — transiently rejectable right after create, so callers should retry |
-| `AddTagExtendedPropertiesAsync` | ✅ | ✅ | live-verified 2026-06-22 over gRPC (`HistoryService.AddTagExtendedProperties`, write-enabled session). NOTE: reading a written prop back via `GetTagExtendedPropertiesAsync` can hit a shared-parser evidence gap (value marker `0x01` vs the captured compact-string `0x09`); the write itself is confirmed. gRPC also exposes `DeleteTagExtendedProperties` (WCF delete was server-blocked) |
-| `GetConnectionStatusAsync` | ✅ | ❌ | synthesized from an authenticated probe — no dedicated RPC on either transport (gRPC `PingServer`/`GetHistorianConsoleStatus` could synthesize it) |
+| `AddTagExtendedPropertiesAsync` | ✅ | ✅ | live-verified 2026-06-22 over gRPC (`HistoryService.AddTagExtendedProperties`, write-enabled session); a written prop now round-trips through `GetTagExtendedPropertiesAsync` (the multi-property parser fix above). gRPC also exposes `DeleteTagExtendedProperties` (WCF delete was server-blocked) |
+| `GetConnectionStatusAsync` | ✅ | ✅ | live-verified 2026-06-22 over gRPC — measured from the handshake (`OpenConnection` yields a storage-session GUID ⇒ connected). No dedicated RPC on either transport; store-forward connectivity stays false (D2-gated) |
 | `ReadBlocksAsync` | ❌ | ❌ | `StartBlockRetrievalQuery` never captured on either transport — throws `ProtocolEvidenceMissingException` |
 
 In short: **WCF is the broad, mature surface** (every config write, events, SQL,
@@ -116,9 +116,10 @@ confirming rows awaits an event-bearing 2023 R2 server. The remaining 🔌 row
 into a gRPC orchestrator + live-capture), not protocol-discovery — but per
 "capture first, never guess wire bytes" it stays untooled until verified live. The
 natural production pattern today: `RemoteGrpc` now covers reads,
-`AddHistoricalValuesAsync`, and the tag-config writes (create/delete/rename/extended
-properties, live-verified) — use WCF for SQL, events, and reading extended
-properties back until those gRPC gaps close.
+`AddHistoricalValuesAsync`, the tag-config writes (create/delete/rename/extended
+properties, including read-back), and connection status — all live-verified. Use
+WCF for SQL (server-walled on gRPC) and event reads/sends (gRPC event rows are
+long-poll-blocked pending an event-bearing server).
 
 > A 2023 R2 server reports History interface version 12 (vs. 11 on 2020). The
 > connect-time version gate accepts both — they are byte-compatible — so gRPC