feat(native): PR1A — fixed native baseline, buffer reduction, diagnostics

[mrmidi]

PR1A — Native Fixed Baseline

Base: pr0/native-build (stacked PR chain)
fptn submodule: fd56bb8 (pr1a/ios-native-baseline)

Socket buffers

• Removed conflicting 4 MiB (Connect) and 1 MiB (RunInternal) TCP buffer assignments — both commented out for easy restoration
• First experiment: kernel default (no explicit value). Isolates the effect of removing the conflicting settings.
• ios_socket_buffer_bytes Conan option on the fptn package (allowed: 0, 262144, 524288). Changing it changes the Conan package ID and recompiles the native library.
• Build script passes -o "fptn/*:ios_socket_buffer_bytes=N" to every conan install and validates the value
• Buffers applied before TCP connect (may influence window negotiation)
• Effective values queried after connect via Boost.Asio get_option (cross-platform); failure stores 0
• Requested values always reflect what the build asked for; failed set_option increments socket_buffer_set_error_count
• Both requested and effective values + error count exposed in status struct (8 new fields)

Beast reader

• 64 KiB initial reserve with a 256 KiB WebSocket message limit (was 4 MiB reserve)

Packet path

• Removed SPDLOG_WARN + two Mach task_info syscalls from packet_callback_adapter (fired every 500 packets)
• Atomic counters remain for getStatus() reporting; unused locals removed

Concurrency

• Renamed thread_number → concurrency_hint (io_context hint, not thread count)
• Set to 1 on TARGET_OS_IOS, 4 elsewhere
• The wrapper already drives the context from one native thread

Process-wide lifecycle counters

• static std::atomic<int>: live_clients_, active_reader_coroutines_, active_sender_coroutines_
• RAII AtomicActivityGuard handles normal returns, exceptions, and co_return
• live_clients_ decrements after Stop() + ioc_.stop() complete
• PR1C will use these for a teardown barrier

Build manifest

• ios_socket_buffer_bytes added to manifest + cache validation

Wrapper status struct

8 new fields in WebsocketClientBridgeStatus (both app + tunnel Swift wrappers):
requestedRcvbufBytes, requestedSndbufBytes, effectiveRcvbufBytes, effectiveSndbufBytes, liveClients, activeReaderCoroutines, activeSenderCoroutines, socketBufferSetErrorCount

Unchanged (later PRs)

• Queue: 256 packets, try_send, silent drop → PR1B
• Teardown: detached coroutines, no barrier → PR1C
• Serialization copies → PR5
• Wire protocol → unchanged

Verification

• Native framework (Debug, C++23): built
• Conan option plumbing: verified (value reaches fptn package, changes package ID)
• Xcode Debug build: succeeded
• Tests: 22/22 passed

Stack

PR-1  Measurement safety
PR0   Production native build     (base)
PR1A  Native fixed baseline       ← this PR
PR1B  Queue and batch bounds
PR1C  Native teardown ownership
PR2   Wrapper/provider integration
PR3   C-based binary flight recorder