CI: Add unit tests for classify_changes.cjs and matches()

[flyingrobots]

Context

In PR #283, classify_changes.cjs was updated to export classifyChanges and matches via module.exports. These functions are now testable but have no unit tests.

Scope

• Test matches() glob function: ** recursive, * single-level, literal paths, dots
• Test classifyChanges(): all three tiers, require_full_classification error path, empty file list
• Test edge cases: overlapping patterns, missing policy fields

Acceptance Criteria

• Unit test file (e.g., scripts/__tests__/classify_changes.test.cjs)
• Tests cover all classification tiers and error paths
• Tests run in CI (add to workflow or package.json scripts)