fix(coding-agent): addressed python cleanup review findings

fixed retained-kernel restart and owner cleanup edge cases during recovery and disposal

tracked async user_python hooks during disposal-sensitive execution paths and hardened startup warmup tracking

strengthened cleanup and kernel lifecycle regressions to remove deadlocks, false positives, and timing flakes

packages/coding-agent/test/core/python-kernel-session.test.ts

@@ -1,6 +1,10 @@
 import { afterEach, beforeEach, describe, expect, it } from "bun:test";
 import { disposeAllKernelSessions, executePython } from "@oh-my-pi/pi-coding-agent/ipy/executor";
-import type { KernelExecuteOptions, KernelExecuteResult } from "@oh-my-pi/pi-coding-agent/ipy/kernel";
+import type {
+	KernelExecuteOptions,
+	KernelExecuteResult,
+	KernelShutdownResult,
+} from "@oh-my-pi/pi-coding-agent/ipy/kernel";
 import { PythonKernel } from "@oh-my-pi/pi-coding-agent/ipy/kernel";
 import { TempDir } from "@oh-my-pi/pi-utils";
 
@@ -20,7 +24,7 @@ class FakeKernel {
 		return { status: "ok", cancelled: false, timedOut: false, stdinRequested: false };
 	}
 
-	async shutdown(): Promise<{ confirmed: boolean }> {
+	async shutdown(): Promise<KernelShutdownResult> {
 		this.shutdownCalls += 1;
 		this.alive = false;
 		return { confirmed: true };