filter-files CI hardcodes 2025 in slug template

[andylizf]

Problem

The filter-files workflow fails on all PRs with 2026-dated posts because bin/filterpaths.py hardcodes the year in the slug template:

SLUG_TEMPLATE = "2025-\d\d-\d\d-.+"

This rejects any post file named 2026-*, such as 2026-02-10-evaluation.md.

Affected PRs

• Add blog post: Evaluating the Hardest CS Problems in the Age of LLMs #4 (merged despite CI failure)
• Fix authors and image paths in evaluation post #6 (currently open, CI cancelled/failed)

Suggested fix

Replace the hardcoded year with a wildcard:

SLUG_TEMPLATE = "\d{4}-\d\d-\d\d-.+"