Three clippy warnings surfaced by the final-review workspace clippy
pass that the per-task gates didn't catch:
- design_system.rs::extract_code_fence — replace manual slice
`&after_open[4..]` with `strip_prefix("json")`. Same behaviour,
cleaner intent, satisfies clippy::manual_strip.
- design_system_tests.rs + visual_ref_tests.rs — flatten the inner
`#[cfg(test)] mod tests { ... }` wrapper. The files are already
wired via `#[path = "..."] mod tests;` in their parent modules
(design_system.rs / visual_ref.rs), so the inner wrapper was double
nesting (clippy::module_inception). Matches the established
pattern in concurrent_tests.rs / plan_repair_tests.rs / run_tests.rs.
574 tests still pass. clippy + fmt + cargo build --workspace clean.
84241b7ea2