feat: implement clip deletion via 'd' key and CMD_DELETE command

e2e/test.ts

@@ -1,6 +1,7 @@
 import { execSync, exec, ChildProcess } from "child_process";
 import * as path from "path";
 import * as fs from "fs";
+import { testDeleteClip } from './test_delete_clip';
 
 const PROJECT_DIR = path.resolve(__dirname, "..");
 const ENGINE_BIN = path.join(PROJECT_DIR, "engine/looper");
@@ -1184,7 +1185,8 @@ async function main(): Promise<void> {
 		testStressRandomUsage,
 		testKeyPressLatency,
 		testStatusFifoLevelLine,
-		testVUMeter
+		testVUMeter,
+		testDeleteClip
 	];
   let passCount = 0;
   let failCount = 0;