Windows: emit vulkan-1 (not vulkan) in the static-link manifest (#103)

cmake/transcribe-install.cmake records `vulkan` into transcribe-link.json's
system_libs on every OS, but Windows' LunarG SDK ships the import lib as
`vulkan-1.lib`. A consumer that reconstructs the link line from the manifest
(the Rust -sys crate, the link_smoke C consumer) then asks MSVC for a
nonexistent `vulkan.lib` and dies with LNK1181: cannot open input file
'vulkan.lib'.

The in-tree ggml-vulkan target links fine because it uses
find_package(Vulkan) -> Vulkan::Vulkan (an absolute path); only the
hand-written manifest reconstruction hardcodes the Unix basename.

Emit `vulkan-1` under if(WIN32) and `vulkan` otherwise, matching how
whisper-rs-sys resolves the same import lib. Non-Windows output is byte
identical.

Co-authored-by: Morrison Liu <morrison@Morrisons-Mac-mini.local>