Stabilize and migrate SOS harness coverage

[steveisok]

Summary

Layer 3 of the native SOS test stack. Depends on #6000.

• migrates the reviewed command-focused coverage and parsing tests onto the stabilized harness
• adds explicit command capability filters and cross-platform corrections without Helix or shard plumbing
• enables .NET 11 SingleFile+cDAC configurations while retaining the layer-2 validity rules
• adds the ObjectReference oracle for notreachableinrange
• retires DivZero.script, NestedExceptionTest.script, and SimpleThrow.script after replacing their exact exception, source-line, stack, thread, live/dump, breakpoint, and CLRMA assertions
• retains Reflection.script because reflection-boundary and target-invocation behavior remains specialized legacy coverage

Preservation and split

• preserves the newer DumpGen_ArgumentsAndFilters test and FirstObjectOfExactType Assert.NotEmpty guard
• preserves concurrent stdout/stderr drainage and all layer-2 harness/process/path/capture work
• keeps README.md architecture/usage documentation and COVERAGE.md, updating both surgically
• excludes CI, Helix, payload, shard, Arcade, project-local skip, replay attribute, and generated solution changes

Validation

• ./build.sh -configuration Debug -architecture arm64 -rebuild -skipnative
• 25 parsing/capability/validity tests
• 7 focused LLDB live exception and source-stack tests on macOS arm64
• 1 focused dotnet-dump notreachableinrange test on macOS arm64