fix: remove dead code paths from getSlotKey

Simplify getSlotKey to a single 3-arg signature by removing:
- Object-form overload (0 of 21 call sites use it)
- Runtime undefined guard (unreachable due to TS typing)

Both paths had 0% coverage across the entire e2e suite.
The @TODO and an in-progress feature branch confirm this
function is transitional code.

src/renderer/core/layout/slots/slotIdentifier.ts

@@ -6,35 +6,14 @@
  * @TODO Replace this concatenated string with root cause fix
  */
 
-interface SlotIdentifier {
-  nodeId: string
-  index: number
-  isInput: boolean
-}
-
 /**
  * Generate a unique key for a slot
  * Format: "{nodeId}-{in|out}-{index}"
  */
-export function getSlotKey(identifier: SlotIdentifier): string
 export function getSlotKey(
   nodeId: string,
   index: number,
   isInput: boolean
-): string
-export function getSlotKey(
-  nodeIdOrIdentifier: string | SlotIdentifier,
-  index?: number,
-  isInput?: boolean
 ): string {
-  if (typeof nodeIdOrIdentifier === 'object') {
-    const { nodeId, index, isInput } = nodeIdOrIdentifier
-    return `${nodeId}-${isInput ? 'in' : 'out'}-${index}`
-  }
-
-  if (index === undefined || isInput === undefined) {
-    throw new Error('Missing required parameters for slot key generation')
-  }
-
-  return `${nodeIdOrIdentifier}-${isInput ? 'in' : 'out'}-${index}`
+  return `${nodeId}-${isInput ? 'in' : 'out'}-${index}`
 }