fix(platform-ios): gracefully stop XCTest agent

[mrousavy]

What is this?

Harness now ends the iOS XCTest permission agent gracefully when a test run finishes, instead of immediately signalling xcodebuild to stop. Previously, normal teardown sent SIGTERM to the long-running xcodebuild test-without-building session while its UI test was still active, interrupting an otherwise-passing agent session and leaving stray simulator and xcodebuild processes behind.

How does it work?

The on-device XCTest agent gains a /shutdown endpoint. When it receives the request it flips an internal flag, its session loop exits on the next tick, and the UI test completes on its own so xcodebuild finishes and tears down its own child processes. During teardown the platform controller asks the agent to shut down first and waits, bounded by a timeout, for the process to exit. If the request fails or the agent does not stop in time, Harness falls back to the existing SIGTERM/SIGKILL termination. The shutdown timeout is raised to accommodate the slower-but-clean exit.

Why is this useful?

Test runs finish without cutting off a healthy agent session, and fewer orphaned simulator and xcodebuild processes survive teardown — reducing flakiness and resource leaks across consecutive iOS runs.

[vercel]

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