feat: add nyx linter tool with multi-language support

[elicpeter]

Add nyx

Adds nyx (source), a local-first, cross-language SAST tool with cross-file taint tracking.

Languages: Python, JavaScript, TypeScript, Java, PHP, Ruby, Rust, Go, C, C++

What it does: Runs taint analysis headless for CI (SARIF output, GitHub Code Scanning compatible) or serves findings to a local browser UI with a flow visualiser, triage workflow, and custom rule editor. Triage state persists to .nyx/triage.json and commits alongside your code. No cloud, no account required.

🛠️ Tool Requirements

• I have not changed the README.md directly. (New tools go in data/tools/)
• The tool has more than 20 stars on GitHub (or similar impact).
• The project has existed for at least 3 months.
• The project is actively maintained.
• The description in the YAML file is under 500 characters.