stdlib: RunFile fails to resolve absolute script paths #259

On current main (444ae5e), py.RunFile cannot resolve an absolute filename with the default compile options. resolveRunPath joins every input to an entry in the search path before checking whether the result is absolute; joining the default "." with "/tmp/script.py" drops the leading slash.

Reproduction on Linux/arm64, Go 1.27.1:

ctx := py.NewContext(py.DefaultContextOpts())
defer ctx.Close()
// Create /tmp/script.py containing: value = 42
_, err := py.RunFile(ctx, "/tmp/script.py", py.CompileOpts{}, nil)

Actual: FileNotFoundError despite the file existing. Passing "script.py" with CompileOpts{CurDir: "/tmp"} works.

Expected: the absolute path is tried directly, independently of the current directory and sys.path, as the resolver's comment describes. This also matters when embedding gpython and supplying paths obtained from a file picker or filepath.Abs.

I am preparing a focused fix and regression tests. AI coding assistance is being used for reproduction, implementation, and validation.