Summary
- Migrates Mojo code off legacy parametric closures (`capturing[_]`, `@__parameter` / `@parameter`, `api[fn](args)`) onto value-taking unified closures (`api(args, fn)` with `{imm}` / `{mut}` / `{var}` / named capture lists).
- Use when removing parametric overloads, fixing "capturing thin" conversion errors, rewriting nested launch/callback closures, or migrating any API that took a comptime function parameter.
- Also use when CI SIGSEGVs while compiling a Mojo object with `compile_offload_closure func must be fully bound` — that is host elaboration; verify with `kgen -elaborate`, not remote GPU execution.