ADR-0002: Fold heading runs into the composition, keeping the last heading's comp_id

Pinned copy. The canonical file is sggs-data/docs/adr/0002-comp-id-keep-last-regroup.md at commit c36e317 — edit it there. This wiki publishes it by pin (ADR-0012); a newer version arrives as a reviewed bump of docs-site/sources.lock.json.

ADR-0002: Fold heading runs into the composition, keeping the last heading’s comp_id

Status: accepted (2026-09-15)

Context

Every heading line had its own comp_id, so a title line followed by a separate ੴ invocation became an orphan one-line composition; the shabad sheet never showed the printed title (e.g. Ang 712). 677 such orphans corpus-wide.

Decision

A run of consecutive heading lines opens ONE composition with the body it introduces (build_corpus.py post-pass 1b). The run adopts the comp_id of its last heading — the one already holding the body — so no body line’s comp_id changes; vacated ids become permanent gaps. Rejected the alternative (contiguous renumber), which would break every stored bookmark/deep link. Three closing rubrics are excluded and stay one-line comps.

Consequences

Distinct comps 5,380 → 4,706 with gaps; max stays 5,380. Saved verses, Spotlight ids, deep links, and analytics keyed on comp_id remain valid. Proven by pipeline/verify_regroup.py (scripture byte-identical).