docs: clarify local development setup

[gbsierra]

Checklist

• Read CONTRIBUTING.md.
• PR title is short and non-generic.
• PR only implements a single feature or fixes a single bug.
• Tests passing (uv run pytest tests)?
• Lint / pre-commits passing (pre-commit run --all-files)?

Description

This PR improves local development onboarding.

It updates CONTRIBUTING.md with supported development environments, required
tools, and the just doctor setup check.

It also adds just doctor, which checks common local requirements before
contributors start the full development stack.

Related Issues

Fixes #2827

Screenshots / Recordings

Git Bash:

WSL:

Steps to QA

1. Run:

just doctor

2. Confirm it reports available and missing tools.

3. After all checks pass, run:

just cluster up -d --seed

4. Confirm the app is available at http://localhost:80.

---

Summary by cubic

Clarifies local development setup and adds a just doctor check to catch missing tools early. This reduces setup issues across macOS, Linux, and WSL2.

• New Features
  • Added just doctor (via scripts/dev-doctor) to validate local prerequisites: OS support, bash, docker + docker compose, curl, git, jq, node, openssl, pnpm, uv, just, and Docker daemon availability. Prints clear next steps and exits non-zero on failures.
  • Detects native Windows shells and recommends WSL2; supports macOS, Linux, and WSL2.
  • Updated CONTRIBUTING.md with supported environments, required tools, WSL2/Docker guidance, quick start using just doctor and just cluster up -d --seed, seeded users, and helpful just cluster commands.
  • Added doctor target to justfile.

^{Written for commit 3e779a0. Summary will update on new commits.}

[zeropath-ai]

✅ No security or compliance issues detected. Reviewed everything up to 3e779a0.

Security Overview

• 🔎 Scanned files: 3 changed file(s)
• 🔗 Scan Link: https://zeropath.com/app/repositories/00dffd6c-8834-4dc9-b6d8-b44cd1622986?scanId=30ab4234-991e-4c2b-aed4-17bc7f5edf7d&codeScanTypes=PrScan&tab=issues

Detected Code Changes

Change Type	Relevant files
Configuration changes	► CONTRIBUTING.md     Update local development setup instructions     Add prerequisites for development     Update seeded user information     Add useful commands for development ► justfile     Add doctor command
Enhancement	► scripts/dev-doctor     Implement script to check development environment prerequisites

[cubic-dev-ai]

No issues found across 3 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}