"integrated" in the sense that the SDK comes with a compiler, but it's not integrated in the same sense as OpenGL where the compiler is part of the driver.

If you can compile that code, then you necessarily have the compiler at hand. You can't make a simple single code file example though. The build system has to get involved somehow.

FWIW, I think this is a good thing. Any non-trivial 3D project is going to involve some kind of asset baking sooner or later, which makes the barrier of entry to that negligible. At the same time, driver-driven compilation is just too convenient and sticky. That's a bad combination.

SPIR-V is an intermediate bytecode format. That bytecode is the data that you use in the Vulkan API, and under the hood your graphics drivers compile that bytecode into the device-specific native shader binary that runs on the graphics hardware.

Vulkan doesn't come with any tools to generate that bytecode though. Foreign shader language (like HLSL, GLSL, etc) to SPIR-V compilers exist, and various graphics toolchains can generate SPIR-V. https://github.com/KhronosGroup/SPIRV-Tools does have tools to validate and optimize bytecode.

edit: i lied apparently - the SPIRV-Tools does have an assembler that translates text such as the "Corresponding SPIR-V" at https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.htm... to bytecode. However, that's not something you'd want to write manually, especially if you're used to something like GLSL.