Fix Errors

When you're working in the Warp Rust codebase and hit compilation errors, clippy warnings, or test failures, this walks you through fixing them. It covers the standard stuff like unused imports and type mismatches, but also handles WASM-specific errors where filesystem code needs gating behind the local_fs feature flag. The real value is having all the presubmit commands in one place, from individual cargo fmt and clippy invocations to running filtered nextest suites. It's basically the debugging checklist you'd build yourself after a few weeks on the project, plus the incantations for WASM clippy and clang-format that you'd otherwise have to dig out of CI configs.