[BUG]: PII scan reports Chrome User-Agent versions as public IP addresses #167

What happened?

The ip_addresses PII check reports a Chromium User-Agent version as a non-RFC1918 IP address. Since Chrome 101, Chromium's reduced User-Agent writes every version as <major>.0.0.0, so any skill that documents or sets a browser User-Agent gets a [PII-MEDIUM] Non-RFC1918 IP address finding for Chrome/140.0.0.0, HeadlessChrome/151.0.0.0, Edg/140.0.0.0 or OPR/122.0.0.0.

Expected: a product token followed by a version, as in an HTTP User-Agent header (product "/" product-version), is not reported. _is_version_literal already exempts version labels (version = "4.4.0.1") and package artifacts (pkg-4.5.0.0.whl), but it has no rule for this form.

I found it by running skillevaluator tier1 --no-llm over my own skills. A browser-automation skill got one finding from a docstring, HeadlessChrome/151.0.0.0 -> Chrome/151.0.0.0.

Reproduction steps

ua-skill/SKILL.md:

---
name: ua-skill
description: Fetch a page with a desktop Chrome user agent. Use when a site rejects the default client.
license: Apache-2.0
metadata:
  author: Jane Doe <[email protected]>
---

# UA skill

Send this header:

```
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/140.0.0.0 Safari/537.36
```

Edge reports `Edg/140.0.0.0` too.

$ skillevaluator pii-scan ua-skill
...
  1. [PII-MEDIUM] Non-RFC1918 IP address: 140.0.0.0 — 2 occurrences (SKILL.md lines 14, 17)
     File:    SKILL.md:14
     Check:   ip_addresses
     Content: User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHT...
     Fix:     Use private IP (10.x.x.x, 192.168.x.x) or placeholder like 0.0.0.0

The finding is non-blocking, but it adds noise to every report for a skill that works with browsers, and its suggested fix (replace the value with a private IP) would make a real User-Agent string wrong.

SkillEvaluator version or commit

main at a2636b2

Environment

Fedora 44, Python 3.12.14 through uv sync --all-extras from a clone. No provider configured.