fix(dflash): suppress compiler warnings — remove unused var, var→let

- DFlashIntermediateDumper.swift: remove unused `totalElements` local
- DFlashRuntime.swift: `var targetCache` → `let targetCache` (never reassigned)

Author: github-actions[bot]

Sources/DFlash/DFlashIntermediateDumper.swift

@@ -42,7 +42,6 @@ public enum DFlashDumper {
         eval(floatArr)
 
         let shape = (0..<floatArr.ndim).map { floatArr.dim($0) }
-        let totalElements = shape.reduce(1, *)
 
         // Build spec-compliant .npy header: shape must be a Python tuple,
         // spaces pad before the final newline byte.

Sources/DFlash/DFlashRuntime.swift

@@ -329,7 +329,7 @@ public enum DFlashRuntime {
 
         let draftBackend = DFlashDraftBackend()
 
-        var targetCache = makeTargetCache(targetModel: targetModel)
+        let targetCache = makeTargetCache(targetModel: targetModel)
 
         let draftCache = draftBackend.makeCache(
             draftModel: draftModel,