kernel/build.home references nonexistent src/kernel.home

Context

kernel/build.home declares its kernel executable with:

const kernel = b.addExecutable(.{
    .name = "home-kernel",
    .root_source_file = b.path("src/kernel.home"),
    .target = target,
    .optimize = optimize,
});

But kernel/src/kernel.home does not exist. The actual kernel entry files in the repo are:

• kernel/src/main.home (470 LOC)
• kernel/src/kernel_main.home (568 LOC)
• kernel/src/kernel_stub.s

So this build file cannot succeed as-is.

Scope

• Decide which entry file is canonical (main.home vs kernel_main.home) — they look like duplicates of each other
• Fix kernel/build.home to reference the correct file
• Delete the redundant entry file (or merge them) so contributors don't have to guess
• If build.home is itself dead code (the actual build path is scripts/build-home-zig.sh), either fix it or delete it — having a broken build entry that "looks canonical" is misleading

Related

• Build script consolidation (separate issue) should pick one canonical build path so we don't have build.home, build.config, build_config.home, scripts/build-*.sh all competing