chore(deps): bump pygments via lockfile-only update (#62)

## Summary
Resolves the **pygments** Dependabot alert via a lockfile-only update
(`uv lock --upgrade-package pygments`). pygments goes 2.19.2 → 2.20.0.

## Not addressed here
- **pytest** (alert #6) — patched in 9.0.3, but `pyproject.toml` pins
`pytest<9.0.0`. Needs a major bump (8.x → 9.x) to the dev dep
constraint, plus any test-compat fixes.

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: B4nan