Fix generated docs for distribution, not just for building docs

[kainino0x]

Fix the typedoc comments in generated/ instead of only in tsdoc-src, and generate docs directly from dist/index.d.ts instead of webgpu.ts.

Also:

• Move manually-written types for uncapturederror into the manually-written section at the top
• Split bitflags types from vars, so that docs can link to them