feat: devex, add Makefile, ruff config, pre-commit hooks, editorconfi…

[OutThisLife]

What does this PR do?

Adds a standard development toolchain. No source files are changed — the ruff config and pre-commit hooks exist for contributors to opt into locally, and the CI lint job is non-blocking (continue-on-error: true) until a follow-up formatting PR lands.

Related Issue

N/A

Type of Change

• ♻️ Refactor (no behavior change)

Changes Made

• Makefile — setup, sync, clean, lint, fmt, check, test, test-fast, test-watch, dev-cli, dev-gateway
• pyproject.toml — ruff lint/format config, added ruff + pre-commit + watchfiles to dev deps
• .pre-commit-config.yaml — ruff + trailing whitespace + merge conflict checks
• .editorconfig — cross-editor defaults (4-space Python, 2-space YAML, tabs for Makefile)
• .github/workflows/tests.yml — added non-blocking lint job with uvx ruff, added uv cache to test job

How to Test

1. make setup creates venv + installs deps + installs pre-commit hooks
2. make test runs the full test suite
3. make lint shows current violations (expected — no formatting pass yet)
4. make fmt auto-fixes lint + format on any files you're working on

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run make test and all tests pass
• I've tested on my platform: Ubuntu 24.04 (WSL2)

Documentation & Housekeeping

• Docs updates (README, CONTRIBUTING.md, AGENTS.md) deferred to follow-up PR to keep this diff minimal