feat: cancel active native commands

[jacklv-coder]

Summary

• bridge Swift Task cancellation through the serial native executor and runtime driver
• terminate the active guest command and confirm authoritative EXITED state before returning CancellationError
• fail closed when native cleanup cannot be confirmed, while keeping the runtime ready after successful cancellation
• pin the published iSH ABI.4 package containing the embedded signal-interrupt fix
• add cancellation/recovery unit coverage, public-ABI.4 RootFS smoke coverage, and synchronized Chinese/English documentation

Validation

• swift test — 122 tests, 0 failures
• real RootFS swift test — 122 tests, 0 skips, 0 failures
• strict-concurrency build with warnings as errors
• documentation mirror/link/anchor checks
• shell syntax and git diff --check
• arm64 Simulator final link
• unsigned arm64 device final link
• Demo build
• public ABI.4 RootFS smoke — 14/14 checks, including active-command cancellation and post-cancellation recovery
• Codex CR of the complete diff — no P1/P2 findings

[chatgpt-codex-connector]

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