feat: add address sanitizer, persistent FIFO fds, and latency test

e2e/test.ts

@@ -71,8 +71,8 @@ function writeFifoCommand(cmd: string): void {
 
 function setupTest() {
   process.stdout.write("  Killing stale processes...\n");
-  runNoThrow("pkill -9 -x looper");
-  runNoThrow("pkill -9 -x looper-client");
+  runNoThrow("pkill -15 -x looper");
+  runNoThrow("pkill -15 -x looper-client");
   runNoThrow("pkill -9 -x jack_capture");
   runNoThrow("tmux kill-session -t looper 2>/dev/null || true");
   process.stdout.write("  Checking JACK...\n");
@@ -90,8 +90,8 @@ function teardownTest() {
     fs.closeSync(cmdFifoFd);
     cmdFifoFd = null;
   }
-  runNoThrow("pkill -9 -x looper");
-  runNoThrow("pkill -9 -x looper-client");
+  runNoThrow("pkill -15 -x looper");
+  runNoThrow("pkill -15 -x looper-client");
   runNoThrow("pkill -9 -x jack_capture");
   runNoThrow("tmux kill-session -t looper");
 }
@@ -911,13 +911,13 @@ async function testStressRandomUsage(): Promise<void> {
         throw new Error("Engine crash during stress test");
       }
 
-      // Check TUI pane integrity (non‑empty, has selection line)
+      // Check TUI pane integrity (non‑empty, at least has header and a cell)
       let pane = tmuxCapturePane("looper", "0");
       if (!pane || pane.trim() === "") {
         await wait(200);
         pane = tmuxCapturePane("looper", "0");
       }
-      if (!pane || !pane.includes("Selected:")) {
+      if (!pane || !pane.includes("JACK Looper") || !pane.includes("   0")) {
         console.log(`  FAIL: TUI pane appears corrupted at key ${keysSent}`);
         console.log("  Pane:\n" + (pane ? pane.slice(0, 1000) : "(empty)"));
         teardownTest();
@@ -940,6 +940,67 @@ async function testStressRandomUsage(): Promise<void> {
   teardownTest();
 }
 
+async function testKeyPressLatency(): Promise<void> {
+  console.log("\nTest: KEY PRESS LATENCY (50 toggles, check for exponential slowdown)");
+  setupTest();
+  const engine = await startEngine();
+  await startClientInTmux();
+  openCmdFifo();
+  await wait(500);
+
+  const ITERATIONS = 50;
+  const LATENCY_WARN = 500;   // warn if >500ms
+  const LATENCY_FAIL = 5000;  // fail if >5s
+
+  let latencies: number[] = [];
+  let prevState = "IDLE";
+
+  for (let i = 0; i < ITERATIONS; i++) {
+    // Determine which state we expect after toggle
+    const expectNext = (prevState === "IDLE") ? "R" : "L";
+    const startTime = Date.now();
+    tmuxSendKeys("looper", "0", "t");
+    const pane = await waitForPaneText(expectNext, 10000);
+    const elapsed = Date.now() - startTime;
+    latencies.push(elapsed);
+
+    // Log periodic summary
+    if (i % 10 === 9) {
+      const avg = latencies.slice(i-9, i+1).reduce((a,b)=>a+b,0) / 10;
+      console.log(`  Iteration ${i+1}: avg last 10 = ${avg.toFixed(0)} ms, last = ${elapsed} ms`);
+    }
+
+    if (elapsed > LATENCY_FAIL) {
+      console.log(`  FAIL: Iteration ${i+1} latency ${elapsed} ms exceeds ${LATENCY_FAIL} ms`);
+      engine.kill(); teardownTest();
+      throw new Error(`Latency exceeded fail threshold at iteration ${i+1}`);
+    }
+
+    if (elapsed > LATENCY_WARN) {
+      console.log(`  WARN: Iteration ${i+1} latency ${elapsed} ms > ${LATENCY_WARN} ms (possible slowdown)`);
+    }
+
+    // Toggle state for next expectation
+    prevState = (prevState === "IDLE") ? "LOOPING" : "IDLE";
+    await wait(200);  // brief cooldown
+  }
+
+  // Check for trend: if last 10 avg > 3x first 10 avg → exponential
+  const first10Avg = latencies.slice(0,10).reduce((a,b)=>a+b,0) / 10;
+  const last10Avg  = latencies.slice(-10).reduce((a,b)=>a+b,0) / 10;
+  console.log(`  First 10 avg: ${first10Avg.toFixed(0)} ms, Last 10 avg: ${last10Avg.toFixed(0)} ms`);
+
+  if (last10Avg > 3 * first10Avg && last10Avg > 500) {
+    console.log(`  FAIL: Latency grew from ${first10Avg.toFixed(0)} ms to ${last10Avg.toFixed(0)} ms (exponential pattern)`);
+    engine.kill(); teardownTest();
+    throw new Error("Exponential latency increase");
+  }
+
+  console.log("  PASS: No exponential latency growth");
+  engine.kill();
+  teardownTest();
+}
+
 async function main(): Promise<void> {
   console.log("=== Looper E2E Tests ===\n");
 
@@ -956,7 +1017,8 @@ async function main(): Promise<void> {
 	 */
 		testRecordOnHighRow, 
 		testRecordMoveRecord,
-		testStressRandomUsage
+		testStressRandomUsage,
+		testKeyPressLatency
 	];
   let passCount = 0;
   let failCount = 0;