refactor!: delete the input.link runtime mirror

The linkStore is now the single source for slot connectivity in both
directions. The NodeInputSlot.link field and all runtime write sites are
gone; a read-only prototype getter derives the id from the store and
fires warnDeprecated as extension migration telemetry (no setter, so
writes throw). Wire format unchanged: serialization derives
inputs[].link from the store.

The mirror-carried association machinery is reworked rather than
papered over: fixLinkInputSlots consumes the serialized graph data
(where node.configure reorders inputs in place), dynamicWidgets' group
rebuilds carry slot-to-link association in a WeakMap refreshed from the
store, reorderSubgraphInputs captures outer links by pre-reorder index,
and link deduplication selects survivors from the store registration -
repairInputLinks is deleted because the derived view cannot be
inconsistent.

Extension migration: read via node.isInputConnected(slot) /
node.getInputLink(slot); mutate via node.connect() /
node.disconnectInput().

docs/architecture/link-topology-store.md

@@ -105,11 +105,9 @@ subgraph-definition GC unregister whole graphs
 
 This design covers link topology (endpoints, type, chain terminus).
 Link visual state (`color`, path caches) and the layout store's link
-_geometry_ records are out of scope. The `output.links` mirror has since
-been deleted — the store is the single source for output-side
-connectivity (see
-[output slot connectivity](output-slot-connectivity.md) Decision 6). The
-`input.link` slot mirror remains the litegraph-native representation
-un-migrated consumers read; extracting it is the `SlotConnection`
-component work in the [ECS migration plan](ecs-migration-plan.md), not
-part of this store.
+_geometry_ records are out of scope. The `output.links` and `input.link`
+slot mirrors have since been deleted — the store is the single source
+for slot connectivity in both directions (see
+[output slot connectivity](output-slot-connectivity.md) Decision 6);
+the remaining fields are deprecated warning getters kept as extension
+migration telemetry.

docs/architecture/output-slot-connectivity.md

@@ -123,10 +123,20 @@ a mirror read plus a `slotFloatingLinks` scan), widget value propagation
 (`widgetValuePropagation`), and matchType link revalidation
 (`dynamicWidgets.changeOutputType`).
 
-## Decision 6: Delete the mirror (implemented)
+## Decision 6: Delete the mirrors (implemented; extended to `input.link`)
 
 The runtime `output.links[]` field and all nine of its write sites are
-deleted. The store is the single source; litegraph internals read through
+deleted. The same recipe has since been applied to `input.link`: the
+field is a deprecated warning getter, litegraph and app code read through
+the slotLinks input helpers (`inputHasLink`, `inputLinkId`, `inputLink`)
+or `node.isInputConnected` / `node.getInputLink`, serialization derives
+`inputs[].link` from the store, and the mirror-carried association
+shuffles were reworked — `fixLinkInputSlots` consumes the serialized
+graph data, dynamicWidgets' group rebuilds carry slot→link association
+in a module-scoped WeakMap refreshed from the store, and link
+deduplication selects survivors from the store registration (the
+`repairInputLinks` mirror repair is gone; the derived view cannot be
+wrong). The store is the single source; litegraph internals read through
 the pure helpers in `node/slotLinks.ts` (`outputHasLinks`,
 `outputLinkIds`, `outputLinks`), and `NodeOutputSlot.isConnected`,
 `serialize`, and `configure` derive from the store. Details:
@@ -193,7 +203,6 @@ sites, and field deletion.
 
 Out of scope, each a piece of the deferred `SlotConnection` phase:
 
-- Deleting the `input.link` mirror field (same recipe as Decision 6).
 - Slot entity extraction: `SlotIdentity`, `SlotVisual`, and retiring the
   `NodeInputSlot` / `NodeOutputSlot` class instances and their
   `shallowReactive` graft.