Fix standard-stream inheritance and platform log chunking

[bkaradzic-microsoft]

Follow-up to #233, addressing Gary's original review and the follow-up review.

Changes

• Make persistent private saved/reader descriptors non-inheritable: F_DUPFD_CLOEXEC on POSIX; non-inheritable DuplicateHandle plus _open_osfhandle(_O_BINARY | _O_NOINHERIT) on Windows, excluding private entries from CRT _spawn* serialization as well as kernel inheritance.
• Use pipe2(O_CLOEXEC) on Android. Keep the checked pipe/fcntl fallback on Apple, which has no pipe2.
• Save and restore target inheritance flags during redirection, Stop, and rollback. Preserve Windows standard-handle behavior, including unavailable GUI descriptors (_get_osfhandle returning -2).
• Preserve Windows CRT translation modes for targets with valid handles during active redirection and restoration. Tee already-translated bytes through binary private descriptors, without a second translation. Decode UTF-16 only for platform diagnostics, retaining incomplete code units/surrogate pairs between reads and replacing malformed input.
• Enforce byte limits for complete and unterminated lines: 3,800 bytes on Windows/Android, 1,023 bytes for Apple default output, and 255 bytes for Apple error output. Preserve UTF-8 boundaries, CRLF, and intentional blank lines; platform chunking does not alter original tee bytes.
• Add lifecycle, byte-preservation, line-boundary, UTF-8/UTF-16, POSIX flag, Windows mode/restoration, and CRT child-startup metadata regressions. Windows child probes run before GTest initialization and are excluded from UWP.

Windows CRT-state limitation

CRT append semantics are not preserved. Private Windows descriptors are reconstructed as binary, non-inheritable descriptors. Translation modes are restored explicitly, but other CRT-only flags, including _O_APPEND, are not retained in those private copies or restored targets. This affects both tee writes and writes after Stop(); applications requiring CRT append semantics must not use Windows forwarding. This replaces the previous description's overly broad claim of full CRT-state preservation.

Process-creation limitation

Applications must serialize child-process creation with Start()/Stop(). Apple's pipe/fcntl fallback, Windows' short-lived CRT mode probe, and descriptor replacement followed by inheritance-flag restoration cannot be atomic with child creation. Persistent private descriptors are non-inheritable while forwarding is active.

Validation

• Windows x64 QuickJS RelWithDebInfo: 16/16 focused logger tests passed across three shuffled runs.
• Both new Windows regressions fail against the previous head, 9b44d12: active modes become binary, and private descriptors are serialized in CRT child-startup metadata.
• CI for 04b808f546cca3256d3b03f886329ad5dc891041 is fully green: 25/25 checks passed (run 35155569100, attempt 2). The initial Android QuickJS failure was an Android Platform 33 SDK archive installation error before compilation; the retry passed without source changes.

[Copilot]

🟡 Changes recommended

Gate or explicitly enable the pipe2 feature declaration for the desktop POSIX test target.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Updates standard-stream redirection to prevent descriptor inheritance and adds platform-specific diagnostic log chunking with regression coverage.

Changes:

• Preserves descriptor flags while enforcing non-inheritance.
• Adds bounded, UTF-8-aware platform log chunking.
• Expands lifecycle, descriptor, and chunking tests.

File summaries

File	Summary
Tests/UnitTests/Shared/StandardStreamLoggerPosix.cpp	POSIX descriptor tests
Tests/UnitTests/Shared/StandardStreamLoggerLines.cpp	Chunking and UTF-8 tests
Tests/UnitTests/Shared/StandardStreamLogger.cpp	Lifecycle and preservation tests
Tests/UnitTests/CMakeLists.txt	Desktop test registration
Tests/UnitTests/Android/app/src/main/cpp/CMakeLists.txt	Android test registration
Core/Foundation/Source/StandardStreamLoggerLines.h	Bounded line processing
Core/Foundation/Source/StandardStreamLogger_Windows.cpp	Windows inheritance handling
Core/Foundation/Source/StandardStreamLogger_Shared.inl	Shared draining and chunk emission
Core/Foundation/Source/StandardStreamLogger_PosixOps.inl	POSIX descriptor and pipe handling
Core/Foundation/Source/StandardStreamLogger_Apple.cpp	Apple log limits
Core/Foundation/Source/StandardStreamLogger_Android.cpp	Android log limits
Core/Foundation/Include/Babylon/StandardStreamLogger.h	API documentation
Core/Foundation/CMakeLists.txt	Foundation source registration

Review details

• Files reviewed: 13/13 changed files
• Comments generated: 1
• Review effort level: Lite

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[bghgary]

[Reviewed by Copilot on behalf of @bghgary]

Concerns inline.