Module Aggregator/Metadata/ArtifactCategoryHeading

Description

Artifact-category and editorial-lede heading helpers extracted from ./heading-rules.ts. Owns:

• EDITORIAL_LEDE_HEADINGS — whitelist of ## headings that carry the journalist's lede paragraph.
• ARTIFACT_CATEGORY_PREFIXES — structural-label H1 prefixes that must not leak into the article <title>.
• normaliseHeadingText / isLedeHeadingMatch — the lede whitelist matcher used by lede-extractor.ts.
• isArtifactCategoryHeading / stripArtifactCategoryAffix — predicates used by the resolver's generic-heading classifier.

Pure leaf module. Re-exported through ./heading-rules.ts for back-compat with existing call sites. Split out of heading-rules.ts in May 2026 to keep both files under the 600-raw-line drift-guard.