Module Aggregator/Metadata/TextTruncate

Description

Byte-budget truncators and sentence-extraction helpers extracted from text-utils.ts to keep both modules under the 600-line drift-guard budget enforced by test/unit/source-file-size.test.js.

This file is the clamping layer of the metadata text pipeline — after shouldSkipDescriptionLine/stripInlineMarkdown produce a candidate description / title, the helpers here apply the SEO-budget shape rules:

• truncateDescription — clamp to DESCRIPTION_MAX_LENGTH on a sentence/word boundary, appending … when truncation occurs.
• truncateExtendedDescription — clamp to the longer EXTENDED_DESCRIPTION_MAX_LENGTH (used by og:description).
• truncateTitle — clamp to TITLE_MAX_LENGTH on a clause boundary, returning '' rather than emitting a mid-sentence ellipsised title.
• extractFirstSentence — return the first complete sentence from a prose paragraph, or '' when no clean terminator is available within the soft-min window.

Bounded-context rules match text-utils.ts:

• No upward imports — pure helpers, no I/O, no globals.
• Deterministic — same input always produces same output.
• Locale-agnostic — operates on raw prose in any of the 14 publishing languages.