Host SOS in a standalone LLDB driver

[steveisok]

Summary

• add a temporary test-only sos-lldb executable on macOS to host SOS through Apple LLDB reliably
• keep the driver source and build target with native test helpers while staging the executable for SOS Helix tests
• scope LLDB command-result routing with a reentrant RAII guard that restores the previous result
• reject invalid LLDB thread IDs at the debugger-service boundary and retain an E_UNEXPECTED CLRMA backstop
• stop batch execution and return a non-zero exit code when an LLDB command fails

Why this layer is separate

This PR contains only the standalone LLDB test-host layer from #5981. Keeping it separate from Helix sharding, harness, documentation, and dependency work makes the temporary host independently reviewable and provides the bottom layer for subsequent stacked changes.

The executable is test infrastructure, is not included in SOS packages, and is temporary until the .NET 11 SDK contains the runtime fix that makes this Apple LLDB workaround unnecessary.

Validation

• ./build.sh -skipmanaged (macOS arm64 Debug)
• successful sos-lldb --no-lldbinit --batch -o version returns 0
• failed batch command returns 1 and prevents later -o commands from running
• an interactive command failure remains nonfatal and later commands still run
• invalid and missing argument checks return 2
• loaded libsosplugin.dylib through sos-lldb and ran soshelp, confirming plugin command output is routed through the scoped result

[Copilot]

Copilot review overview

🟡 Changes recommended

The new sos-lldb driver currently doesn’t reliably surface command failures to callers in --batch mode (exit code remains 0), which can break scripting/CI usage.

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

Review tier: Lite
Findings: 1

New issues introduced by this change (1)

Severity	Finding
	src/​SOS/​lldbplugin/​driver.cpp — The standalone driver currently can't propagate LLDB command success/failure to the caller because…

What changed in this PR

This PR introduces a standalone macOS sos-lldb executable to host SOS via Apple LLDB, while also tightening LLDB command output routing and rejecting invalid CLRMA OS-thread IDs to avoid mis-resolving threads.

Changes:

• Add a macOS-only sos-lldb LLDB driver executable and install it alongside libsosplugin.
• Replace manual SetCurrentResult/ClearCurrentResult with a re-entrant RAII scope that restores the prior SBCommandReturnObject.
• Reject CLRMA thread lookups that resolve to invalid OS thread IDs (0 or -1).

File	Description
src/​SOS/​Strike/​clrma/​managedanalysis.cpp	Rejects invalid OS thread IDs before delegating to CLRMA service or building a ClrmaThread.
src/​SOS/​lldbplugin/​soscommand.cpp	Uses scoped result routing for SOS command execution so output targets the correct command result.
src/​SOS/​lldbplugin/​services.h	Adds LLDBServices::CurrentResultScope RAII guard and removes the previous setter/clearer helpers.
src/​SOS/​lldbplugin/​services.cpp	Applies scoped result routing in extension command execution and LLDBServices::ExecuteCommand.
src/​SOS/​lldbplugin/​driver.cpp	Adds the new standalone sos-lldb driver program for LLDB command hosting.
src/​SOS/​lldbplugin/​CMakeLists.txt	Builds and installs sos-lldb on macOS.

Suppressed comments (1)

src/SOS/lldbplugin/driver.cpp:83

• In --batch mode, failures from -o commands should typically produce a non-zero process exit code (and often stop executing further commands). As written, the driver always returns 0, which can cause scripts to miss command failures.

    lldb::SBCommandInterpreter interpreter = debugger.GetCommandInterpreter();
    bool keepRunning = true;
    for (const std::string& command : startupCommands)
    {
        if (!ExecuteCommand(interpreter, command))

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