refactor(drivers): delete the dead discovered-node injection path (§8.2, #507)

#507 was filed as "injection inert in v3, re-migrate onto the raw subtree".
Reading it, the retained code is not revivable: it resolves equipment from
EquipmentNode.DriverInstanceId UNION EquipmentTags, and BOTH are structurally
empty in v3 (AddressSpaceComposer always constructs EquipmentNode with a null
DriverInstanceId; DeploymentArtifact hard-codes an empty EquipmentTags set).
Removing the guard would have changed a log line and injected nothing. So it
is deleted rather than fixed, and #507 closes as superseded by /raw
browse-commit.

Removed: HandleDiscoveredNodes, PartitionDiscoveredByDeviceHost,
ShouldWarnPartition, PlansRoutingEqual, ApplyDiscoveredPlansForDriver,
_discoveredByDriver, the redeploy re-inject tail, DiscoveredNodeMapper,
DiscoveredInjection, AddressSpaceApplier.MaterialiseDiscoveredNodes,
OpcUaPublishActor.MaterialiseDiscoveredNodes, and the Runtime-local copies of
CapturingAddressSpaceBuilder/DiscoveredNode.

The connect-time discovery loop goes too (StartDiscovery, RediscoverTick,
HandleRediscoverAsync, DiscoveredNodesReady, TriggerRediscovery). With
injection gone it had no consumer, and leaving it would either dead-letter or
keep browsing real devices up to ~15x per connect to drop the result.
ITagDiscovery itself stays — the /raw browse picker drives it through
Commons/Browsing/DiscoveryDriverBrowser, which never went through the actor,
so the picker is unaffected.

deferment.md §4.4 called the 18 DiscoveryInjectionDormantV3 tests "Real —
blocked on #507". They are not: they assert an equipment-rooted graft
(EquipmentRootNodeId == "EQ-1") that v3 cannot produce, so they could never
have unskipped as written. Deleted along with DiscoveredNodeMapperTests, the
CapturingAddressSpaceBuilder tests, and the MaterialiseDiscoveredNodes tests
in AddressSpaceApplierTests/OpcUaPublishActorTests. Runtime.Tests skipped:
31 -> 13.

IHostConnectivityProbe is deliberately NOT resolved here. GetHostStatuses()
has no production call site and nothing writes a DriverHostStatus row, but the
table was re-created in the v3 initial migration, so deleting on inference
would be wrong. Split to Gitea #521 with both options costed.

CLAUDE.md, docs/drivers/{Galaxy,TwinCAT,MTConnect}.md updated — they described
the seam as dead.

Build clean; Runtime.Tests 476 passed / 13 skipped; OpcUaServer.Tests 362
passed / 4 skipped.

docs/drivers/Galaxy.md

@@ -70,7 +70,7 @@ Project root files:
 | Capability | Implementation entry point |
 |------------|---------------------------|
 | `ITagDiscovery` | `Browse/GalaxyDiscoverer.cs` |
-| `IRediscoverable` | `Browse/DeployWatcher.cs` — ⚠️ raised but **unconsumed**; a Galaxy redeploy does not rebuild the address space ([#518](https://gitea.dohertylan.com/dohertj2/lmxopcua/issues/518), [#507](https://gitea.dohertylan.com/dohertj2/lmxopcua/issues/507)) |
+| `IRediscoverable` | `Browse/DeployWatcher.cs` — consumed as an **operator prompt**: a Galaxy redeploy raises a "re-browse" chip on `/hosts`. ⚠️ It does **not** rebuild the address space — re-browse the device under `/raw` and commit ([#518](https://gitea.dohertylan.com/dohertj2/lmxopcua/issues/518)) |
 | `IReadable` | `Runtime/GalaxyMxSession.cs` |
 | `IWritable` | `Runtime/GatewayGalaxyDataWriter.cs` |
 | `ISubscribable` | `Runtime/GatewayGalaxySubscriber.cs` (driven by `EventPump`) |