feat(mqtt): read Sparkplug B array metrics as 1-D OPC UA arrays (lmxopcua#754)

R06:M-5 made Sparkplug *Array leaves unbindable because the ingestor refused
them. The ingestor now decodes the packed bytes_value of all 13 array types
(new SparkplugArrayCodec: LE fixed widths, int64-ms DateTime, uint32-count +
MSB-first BooleanArray, NUL-terminated UTF-8 StringArray; golden vectors are
the spec's examples, reproduced byte-for-byte by SparkplugNet 1.3.10) and
publishes a typed 1-D array through the scalar coercion, all-or-nothing.

Shape uses the fleet's one array model: the tag's platform isArray/arrayLength
keys (ValueRank=1, ArrayDimensions=[arrayLength] or [0] = variable length).
The driver reads them with TagConfigIntent's exact semantics and never rejects
on them, so composer, driver, authoring model and deploy inspector agree
(MqttArrayShapeParityTests). Shape mismatch (array metric on a scalar tag, or
the reverse) is BadTypeMismatch - a String tag no longer gets the packed
buffer as base64; a malformed body or a length differing from a declared
arrayLength is BadDecodingError (MTConnect #627 verdict). Template/DataSet
members of an array type take the same path. Arrays stay read-only (encoder
refuses them; MQTT is not in DriverArrayWriteSupport).

Browser: array leaves are bindable again and state isArray in AddressFields;
the commit mapper writes "isArray": true (no arrayLength). Discovery reports
IsArray/ArrayDim. Docs: Mqtt.md "Array metrics", design table, drivers rule.

Tests: codec (golden + malformed), ingest through the real codec + Dispatch
(the project's MiniBroker never forwards a PUBLISH, so there is no in-process
broker harness), browse, discovery, commit mapper, parity corpus. Mutating the
fix back out fails 18 MQTT + 9 AdminUI tests.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

docs/plans/2026-07-15-mqtt-sparkplug-driver-design.md

@@ -148,7 +148,7 @@ Sparkplug metric datatype (or inferred/authored plain type) → `DriverDataType`
 | DateTime | `DateTime` | DateTime |
 | Bytes, File | `String` (base64/raw fallback, v1) | String |
 | DataSet, Template | **unsupported v1** — skip + warn, or expose raw-JSON as `String` | — |
-| `*Array` variants | element type + `IsArray=true`, `ArrayDim` from birth | ValueRank=1 |
+| `*Array` variants | element type + `IsArray=true`; ArrayDimensions from the tag's `arrayLength` (absent ⇒ variable length, `[0]`) — implemented #754, see `docs/drivers/Mqtt.md` §"Array metrics" | ValueRank=1 |
 
 Live map in `SparkplugDataType.ToDriverDataType()` (`.Contracts`). **Plain mode:** honour an explicit per-tag `dataType` (preferred — inference is brittle); fall back to inferring from the JSON token at `jsonPath` (number→`Float64`/`Int64`, bool→`Boolean`, string→`String`). Int8/UInt8 widen (no OPC UA signed-byte distinction needed).