[flynn-eye]

io.write("123 ") currently writes 123, and strings such as "001.20 " or "0x10 " are reformatted as numbers. The shared write helper calls ToNumber before checking whether an argument is already a string.

Use CheckString directly: string bytes are preserved, while actual numbers still use the existing numberToString conversion. Regression coverage exercises both io.write and file:write, including whitespace, leading zeros, hexadecimal/exponent strings, actual numbers, and the returned file handle.

Fixes #92.

Validation on Go 1.25.0, darwin/arm64:

• Both new regression cases fail on the old helper and pass after the change.
• go test -vet=off -race ./... passes with the lua-tests submodule initialized. Existing tests requiring luac skip because it is not installed; the existing architecture-dependent test also skips.
• go vet -tests=false ./... passes.

Default test vet reports the pre-existing non-niladic ExampleFunction in doc_test.go; the same error was verified on pristine upstream 3f823f8.