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is deleted rather than fixed, and #507 closes as superseded by /raw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/MTConnect.md

@@ -220,8 +220,9 @@ what the driver's cursor expects) is detected **two ways**, both triggering a
 **before** the sequence-gap check (a restart also usually trips the gap, so
 the two need disambiguating, not just OR-ing together). On a changed
 `instanceId` the driver clears its cached probe model and raises
-`OnRediscoveryNeeded` — see [Known limitations](#known-limitations) for why
-that signal currently has no consumer.
+`OnRediscoveryNeeded`, which surfaces a **re-browse prompt** on the AdminUI
+`/hosts` page — see [Known limitations](#known-limitations) for what that does
+and does not do.
 
 ## Browse — free via the universal browser
 
@@ -249,16 +250,20 @@ need re-authoring. See [Deferred](#deferred-not-in-this-build).
 These are real, not placeholders — read them before relying on the driver
 for anything beyond values-and-conditions.
 
-1. **`IRediscoverable` and `IHostConnectivityProbe` have no consumer in the
-   server.** `DriverInstanceActor` wires only `ISubscribable.OnDataChange` and
-   `IAlarmSource.OnAlarmEvent`; nothing in the server subscribes to
-   `OnRediscoveryNeeded` or `OnHostStatusChanged` except `GalaxyDriver`
-   wiring its own internal `DeployWatcher` sub-component. So a restarted
-   Agent (a changed `instanceId`) leaves a stale address space behind an
-   otherwise-Healthy driver. **This is a pre-existing fleet-wide gap
-   affecting every driver that implements either interface** (eight drivers
-   besides Galaxy), not something specific to MTConnect — this build simply
-   surfaced it again.
+1. **A restarted Agent prompts an operator; it does not re-shape the address
+   space.** `DriverInstanceActor` now consumes `OnRediscoveryNeeded`
+   (2026-07-27), so a changed `instanceId` raises a "re-browse" chip against
+   this driver on `/hosts` carrying the reason. It is **advisory**: v3 authors
+   raw tags through the `/raw` browse-commit flow, so until an operator
+   re-browses the Agent and commits, any DataItem that appeared or vanished is
+   not reflected in the served tree. A runtime graft was deliberately rejected
+   — it would materialise nodes nobody approved and no deployment artifact
+   records.
+
+   **`IHostConnectivityProbe` is still unconsumed** — `GetHostStatuses()` has
+   no production call site and nothing writes a `DriverHostStatus` row. That
+   half remains a fleet-wide gap affecting every driver that implements it
+   (Gitea #521).
 2. **`RawTagEntry.DeviceName` is accepted on the wire shape but ignored for
    routing.** One driver instance owns exactly one Agent client scoped by
    `MTConnectDriverOptions.DeviceName` (the top-level config key); the