docs: live-gate round two — truncation note + central proto path both proven (#541)

25 unmappable tags on SITE-A's sa-modbus2 closed both gaps in one setup: chip
25/26 SKIPPED, sample capped at exactly MaxSample=20, tooltip '(+5 more not
shown)'. Trimming to 20 skipped gave 20/21 with NO truncation note, pinning
the off-by-one boundary.

SITE-A is the discriminator for the proto path. Phase 6 partitioned it into
its own Akka mesh -- central's MEMBERS panel lists only central-1/central-2,
and DistributedPubSub does not federate across meshes. The single site-a
reference in central's log is the ClusterClient receptionist, a
point-to-point command path, not gossip. So the report's only route to the
page is TelemetryProtoMapNode -> gRPC -> TelemetryProtoMapCentral, and
central's view tracking a change made solely on the site node is conclusive.

Also corrects round one's claim that the fused central pair meant telemetry
never crossed gRPC -- wrong about this rig. All six ClusterNode rows carry
GrpcPort 4056 and Telemetry__Mode=Grpc; the two 'Telemetry stream to node'
lines that suggested a two-node dial set were startup failure warnings.

Rig restored: test tags deleted, SITE-A redeployed, sa-modbus2 back to 1 tag.

docs/plans/2026-08-05-skipped-tag-visibility-live-gate.md

@@ -3,7 +3,8 @@
 **Date:** 2026-08-05
 **Rig:** local `docker-dev/` (OrbStack), MAIN pair `central-1` / `central-2`, AdminUI `http://localhost:9200`
 **Build under test:** `fix/541-skipped-tag-visibility`
-**Result: PASS**, and the gate found one defect that unit tests did not (§4).
+**Result: PASS.** The gate found one defect unit tests did not (§4). Round two on 2026-08-06 closed
+the two items round one left unproven and corrected a wrong claim about the rig's topology (§6).
 
 ## What needed proving
 
@@ -85,10 +86,47 @@ The three `pymodbus` blobs were restored from the pre-change backup and MAIN red
 shows `13 tags`. The three pre-existing skipping drivers were left exactly as they were — they are the
 rig's own configuration, not this gate's.
 
-## Not proven here
+## 6. Round two (2026-08-06) — truncation note + the central proto path
 
-- The `+N more not shown` truncation note (needs a deployment skipping more than
-  `SkippedTagLedger.MaxSample` = 20 tags; unit-covered only).
-- The central-side proto path — the rig's central pair is fused admin+driver, so the health snapshot
-  never crossed the Phase 5 gRPC telemetry stream. `TelemetryProtoMapCentral`/`Node` are unit-covered
-  round-trip only.
+Both items round one left unproven were closed by one setup, chosen so that a single observation
+settles both. **One correction first:** round one recorded "the rig's central pair is fused
+admin+driver, so the snapshot never crossed the Phase 5 gRPC telemetry stream." That was wrong about
+the rig. All six `ClusterNode` rows carry `GrpcPort 4056`, every node runs `Telemetry__Mode=Grpc`, and
+central dials all six — the two `Telemetry stream to node …` lines seen in round one were startup
+*failure warnings*, not the dial set.
+
+**Setup.** 25 tags with `region: NoSuchRegion` added to `sa-modbus2` on **SITE-A**, joining its one
+good tag (26 total), then SITE-A deployed. SITE-A is the discriminator: Phase 6 partitioned it into
+its own Akka mesh, so central's MEMBERS panel lists only `central-1:4053` and `central-2:4053`.
+DistributedPubSub fans out within one mesh's mediator and does not federate, and the single
+`akka.tcp://otopcua@site-a-1` reference in central's log is the ClusterClient **receptionist** — a
+point-to-point command path, not gossip. So a SITE-A driver's health can reach central's `/hosts` by
+exactly one route: `TelemetryProtoMapNode` → gRPC `TelemetryStreamService/Subscribe` →
+`TelemetryProtoMapCentral`.
+
+**Result — 25 skipped of 26 authored:**
+
+| Fact | Observed |
+|---|---|
+| Chip | `25 / 26 SKIPPED`, `chip-warn` |
+| Driver status | HEALTHY, 0 errors (as ever) |
+| Sample entries in tooltip | **20** (= `SkippedTagLedger.MaxSample`) |
+| Truncation note | **`(+5 more not shown)`** |
+| Skips logged on `site-a-1` | 25 |
+
+That proves the truncation note, and simultaneously proves the proto path: the counts *and* all 20
+sample entries with their RawPath + reason survived the wire.
+
+**Positive control, doubling as the cap boundary.** Five of the 25 broken tags were deleted and SITE-A
+redeployed. Central's page tracked the change made only on the site node — `20 / 21 SKIPPED`, sample
+still 20, and **no truncation note**, correct at exactly `MaxSample` (the off-by-one that would have
+read "+0 more not shown"). A live-updating view of a node with no gossip path is conclusive.
+
+**Rig restored:** all 25 test tags deleted, SITE-A redeployed, `sa-modbus2` back to `1 tag`; the
+deployment revision hash returned to the pre-test `6178a8f3…`.
+
+## Still not proven live
+
+Nothing outstanding from the original two. Remaining unit-only coverage is the ledger's concurrency
+guard (a torn read under a real init/publish interleaving) — inherently hard to force on a rig, and
+the lock makes it a code-inspection matter rather than an observational one.