Diagnostic dump in --smoke-tree-sitter handler

Round 6 (sibling-file approach) still failed on Windows. The smoke
handler reports the same pre-init-state-empty error even though the
build script copied tree-sitter.wasm next to the binary just before
the smoke step ran.

Add a diagnostic dump that prints process.execPath, dirname, the
computed siblingPath, existsSync result, the dir listing, env var,
and globalThis state. Whatever the next CI Windows run shows here is
what we need to fix.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>