docs(handoff): refresh to current state — roadmap exhausted

The handoff doc was anchored at 2026-05-04 (read-path blocker era). Add a
"Current Status (2026-06-22)" section at the top summarizing the full shipped
read/write/config/client-side surface across WCF + gRPC, the 8 remaining gated
items (event-row retrieval, active-SF magnitude, SendEvent capture, SQL wall,
R4.2 edits, ReadBlocks, the disproven DelTep gRPC probe, deferred-by-design),
and what would unblock each. Reframe the old "Active Blocker" as a historical
read-path record; fix the stale 55/55 test count to 321/321 offline.

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

docs/reverse-engineering/handoff.md

@@ -1,6 +1,69 @@
 # AVEVA Historian Managed Driver Handoff
 
-Last updated: 2026-05-04 (write surface live: EnsT2 + DelT + ApplyScaling)
+Last updated: 2026-06-22 (roadmap exhausted — no actionable pure-code tasks remain)
+
+> **Current status supersedes the historical blocker narrative below.** The
+> sections from "Active Blocker" onward are a preserved reverse-engineering
+> record of how the 2020 WCF read/write/event paths were cracked (2026-05-04).
+> They are kept for provenance; they are **not** the live state. Start with
+> "Current Status" immediately below.
+
+## Current Status (2026-06-22) — roadmap exhausted
+
+`docs/plans/hcal-roadmap.md` reachable surface is **complete**, and every plan
+under `docs/plans/` is either DONE or has only gated items left. There are
+**zero actionable pure-code tasks remaining**. Memory anchor:
+`project_roadmap_exhausted_2020wcf`.
+
+**Shipped + live-verified across both transports:**
+
+- **Reads** (WCF + gRPC): `ProbeAsync`, `ReadRawAsync`, `ReadAggregateAsync`,
+  `ReadAtTimeAsync`, `ReadEventsAsync`, `BrowseTagNamesAsync`,
+  `GetTagMetadataAsync`, status helpers (`GetConnectionStatusAsync`,
+  `GetStoreForwardStatusAsync`, `GetSystemParameterAsync`).
+- **Writes**: `EnsureTagAsync` (analog Float/Double/Int2/Int4/UInt4, `ApplyScaling`),
+  `DeleteTagAsync`, `RenameTagsAsync`, `AddTagExtendedPropertiesAsync`, and the
+  M3 historical/backfill `AddHistoricalValuesAsync` (**gRPC-only**, all five
+  analog types golden-tested + live write/read-back).
+- **Config reads** (mostly gRPC): `GetRuntimeParameterAsync`,
+  `GetTagExtendedPropertiesAsync`, `ExecuteSqlCommandAsync` (WCF; gRPC
+  server-walled), `GetServerTimeZoneAsync` (gRPC-only).
+- **Client-side**: M4 R4.1 store-and-forward outbox, R4.4 redundancy,
+  R4.3 measured-idle SF status.
+
+The 2023 R2 **gRPC transport** (`HistorianTransport.RemoteGrpc`, port 32565)
+reuses the proven 2020 WCF byte serializers/parsers unchanged inside protobuf
+`bytes` fields, keyed by the Open2 session handle. Live-verified against a real
+2023 R2 server (History interface v12) — see `reference_2023r2_live_server_access`.
+
+**Everything still open is gated — none is a pure-code task:**
+
+1. **gRPC event ROW retrieval** (`ReadEventsAsync` #2) — chain + StartEventQuery
+   work; `GetNextEventQueryResultBuffer` long-polls on no data. Needs an
+   **event-bearing 2023 R2 server**. Bounded ≤30s, throws on no-row.
+2. **R4.3 active-SF magnitude** — needs an **SF-active server** (D2 storage-engine
+   console handle).
+3. **SendEvent over gRPC** — **capture-gated**: no distinct RPC, framing uncaptured.
+4. **ExecuteSqlCommand over gRPC** — **server-walled** (`CSrvDbConnection`;
+   RegisterTags prime doesn't help). Use WCF for SQL.
+5. **R4.2 revision EDITS** — storage-engine-pipe-only on BOTH transports (the D2 wall).
+6. **ReadBlocks** (`StartBlockRetrievalQuery`) — never captured on either transport.
+7. **DeleteTagExtendedProperties** — server-blocked on BOTH transports. The gRPC
+   multiplexed-channel hypothesis was **PROBED + DISPROVEN 2026-06-22** (merge
+   `c88260c`): GetTgByNm + GetTepByNm primes succeed on one shared write-enabled
+   gRPC channel, yet DelTep is still rejected (native code=1) and the property
+   survives — the working set is native in-process registration state, not the
+   wire session. Pinned by gated negative test
+   `DeleteTagExtendedProperties_OverGrpc_ProbeMultiplexedChannel`.
+8. **Deferred-by-design** items (`write-commands` D1–D3, non-analog tag create,
+   etc.) — bounded out until an explicit customer/user demand signal.
+
+To move any remaining item you need a **different server** (event-bearing or
+SF-active), a **fresh native capture** (SendEvent gRPC framing), or a **demand
+signal** to unlock a deferred item. Live-server gRPC probe recipe: set
+`HISTORIAN_GRPC_HOST`/`_PORT 32565`/`_TLS true`/`_DNSID` + domain creds (strip
+quotes — `reference_wonder_sql_vd03_credentials`) and run the gated
+`HistorianGrpcIntegrationTests`.
 
 ## Project Direction
 
@@ -73,10 +136,12 @@ dotnet build .\Histsdk.slnx --no-restore
 dotnet test .\Histsdk.slnx --no-build --logger "console;verbosity=minimal"
 ```
 
-Current known-good result:
+Current known-good result (2026-06-22):
 
-- Build succeeds.
-- Unit tests pass: 55/55.
+- Build succeeds (0 warnings / 0 errors).
+- Offline tests pass: 321/321 (live gRPC/integration tests skip cleanly without
+  their env vars). Gated live tests add to this when `HISTORIAN_*` /
+  `HISTORIAN_GRPC_*` are set.
 
 The workspace is a Git working tree (origin: gitea.dohertylan.com). Use
 normal git workflow for change tracking; the prior "no working tree, use
@@ -227,7 +292,10 @@ Negative evidence:
 - Running the same managed `ValCl` path through .NET Framework also fails, so
   this is not just a .NET 10 WCF behavior difference.
 
-## Active Blocker
+## Historical: Read-Path Blocker (resolved 2026-05-04)
+
+> Preserved RE record. This was the *original* active blocker; it is long
+> resolved and is not the live state — see "Current Status" at the top.
 
 **Resolved on `2026-05-04`.** The previous blocker — managed `ValCl`
 rejected by the server — had two causes, both now fixed: