test(coding-agent): align retry rollover, flag table, and python detach tests with merged semantics

- retry-cap rollover repro no longer pins which sibling credential the
  session hash starts from; it asserts all four are rolled through
- STRING_VALUE_FLAGS table test accepts value-validating flags that
  reject the consumed token with CliUsageError (--max-time)
- python dispose-detach test follows the eval abort-shield contract:
  runs aborted mid-flight report cancelled even when the kernel races
  to completion

packages/coding-agent/test/agent-session-python-cleanup.test.ts

@@ -493,9 +493,12 @@ describe("AgentSession python cleanup", () => {
 		expect(startSpy).toHaveBeenCalledTimes(1);
 
 		blockedExecution.resolve(OK_EXECUTION);
+		// The dispose abort was requested while the execution was still running;
+		// the executor reports such runs as cancelled even when the kernel races
+		// to completion. Detachment is proven below: the kernel survives, is not
+		// restarted, and keeps serving the surviving session.
 		await expect(firstExecution).resolves.toMatchObject({
-			cancelled: false,
-			exitCode: 0,
+			cancelled: true,
 			stdinRequested: false,
 		});
 		await secondSession.executePython("print('owner-b after detach')");