test(aot): native end-to-end coverage for `home build --compile` and `--bytecode`

Problem

The compile tests counted as passing in PARITY-BUN.md run through JS "bootstrap models", and the doc itself says native parity still needs the real compile pipeline and executable embedding. There is no tests/runtime/native-* compile test, and CachedBytecode.zig is still headed "re-attaches in Phase 12.2".

Evidence (origin/main @ d4b219507)

• docs/docs/PARITY-BUN.md:1461-1468
• packages/runtime/src/jsc/CachedBytecode.zig:1-12
• src/main.zig:3073-3076

Scope

• Add a native test that compiles a small server, copies it to another directory with no home on PATH, runs it and hits it over HTTP.
• Verify the bytecode section exists and is actually used at load time with --bytecode.
• Run upstream bundler_compile.test.ts unmodified on the native runtime.

Acceptance criteria

• The native compile tests pass on macOS and Linux in CI.
• --bytecode measurably reduces startup (numbers recorded in the benchmark issue).

Links

Depends on: #791 Part of #814.