[ts-codegen] Generated SSE procedures should have a return type annotation

[joshmossas]

Environment
arri v0.45.4
node 20.12.2

Reproduction
N/A

Describe the bug
Generated clients with SSE procedures produce this TS error

The inferred type of '<procedure-name>' cannot be named without a reference to '.pnpm/event-source-plus@0.0.6/node_modules/event-source-plus'. This is likely not portable. A type annotation is necessary.

Additional context
The fix is to have generated code add a return type annotation and import from event-source-plus

[joshmossas]

fix in v0.45.5