Clean up stale 0-byte files at repo root

Context

Two empty files committed at repo root that look like leftover build artifacts:

• compile_home_kernel (0 bytes, marked executable)
• pantry_native.o (0 bytes)

scripts/compile_home_kernel.zig exists as the actual source, so the empty compile_home_kernel at root is presumably an old build output. pantry_native.o is presumably a stale linker artifact.

Scope

• Delete compile_home_kernel (0-byte file at root)
• Delete pantry_native.o (0-byte file at root)
• Audit .gitignore and add patterns for build outputs:
  • *.o (compiled object files)
  • Bare executables produced by build scripts (the build dir already covers most of these — check)
• Verify no scripts depend on those files existing at root

Notes

Same pattern showed up in home-lang/home (filed separately there). Worth keeping the cleanup uniform across both repos.