Make lint workflow friendlier on clean setups

[BennettSchwartz]

Summary

make lint currently runs staticcheck ./... but assumes staticcheck is already installed. On a fresh setup, this target fails unless contributors manually install it first.

Why this is a good first issue

• Small developer-experience improvement.
• Localized change in tooling/docs.
• Helpful for first-time contributors.

Proposed work

Make linting workflow self-explanatory and reproducible for fresh environments by either:

1. Teaching make lint to install/use staticcheck automatically, or
2. Adding a dedicated setup target and updating docs so the required install step is explicit.

Acceptance criteria

• A clean environment can follow documented steps and run make lint successfully.
• CONTRIBUTING.md and/or Makefile reflect the intended workflow.
• CI behavior remains unchanged (or improves) for linting.