docs(phase4c): cross-driver 1-D array support + isArray/arrayLength keys + coverage matrix

docs/drivers/S7.md

@@ -140,6 +140,35 @@ Portal under *Protection & Security* for the CPU.
 - **CLI** — [Driver.S7.Cli.md](../Driver.S7.Cli.md) documents the standalone
   read/write/probe CLI for manual checks against a real or simulated CPU.
 
+## 1-D array support
+
+An S7 tag becomes a **1-D OPC UA array node** when its `TagConfig` JSON carries
+`"isArray": true` and `"arrayLength": N` (N ≥ 1).  The canonical rule:
+`isArray: true` + `arrayLength >= 1` → array; `isArray: false` (any length) → scalar.
+
+**Read mechanism** — the driver issues a single `ReadBytesAsync` call over the contiguous
+memory span starting at the declared address for `N × (bytes per element)` bytes, then
+loops over the response buffer decoding each element individually using the same
+reinterpret/box logic as scalar reads.  This keeps wire round-trips at 1 per array tag
+regardless of N.
+
+**Supported element types** — any `S7DataType` that has a scalar decode path today
+(`Bool`, `Byte`, `Int16`, `UInt16`, `Int32`, `UInt32`, `Float32`).  The `ReadBytesAsync`
+network half is a thin `S7.Net` call; the decode half is fully unit-tested.
+
+**Unit test coverage** — `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/` covers
+the contiguous-block read and per-element decode loop.  Integration fixture is down during
+normal dev (the S7 sim is on the shared Docker host but currently offline).
+
+**Live-verify** — integration-fixture-gated (not Mac-verifiable without the S7 sim up).
+
+**Deferrals** — array *writes*, multi-dimensional arrays, per-element historization.  The
+`Timer` / `Counter` address types that are rejected at init for scalars are also excluded
+for arrays.
+
+See [Uns.md §Array tags](../Uns.md#array-tags-1-d) for the cross-driver coverage matrix
+and the UI authoring flow.
+
 ## Further reading
 
 - [`docs/v2/driver-specs.md §5`](../v2/driver-specs.md) — full per-field spec,