`$lib/utils/list-title.ts` is the pure module — `parseTitle` extracts
{prefix, number} from a typed value, `nextNumberFromNumbers` is the
trivial `max + 1`, and `computeNextNumberFromNames` walks a row list,
counts a bare-prefix match as N=0, and falls back to 1 when nothing
matches. The regex requires whitespace between prefix and `#` so
"Compra#5" stays literal (the chip only fires for catalog-curated
prefixes). 19 unit tests cover LT-U-01..05 plus seven boundary cases
(multi-word prefixes, case-insensitive matching, substring near-miss,
trimming, empty input, bare-hash rejection).
`$lib/stores/listTitles.ts` wraps the two SECURITY DEFINER RPCs
(add/remove) and exposes `loadTitleCatalog`, `setDefaultListTitle`
(plain UPDATE on `collectives` — RLS already gates UPDATE to admins),
`fetchTitleSuggestions` (catalog ∪ last 10 distinct shopping_lists.name,
dedup case-insensitive, cap 15) and `computeNextNumber` (driver for the
SQL `name.ilike.<prefix>,name.ilike.<prefix> #%` filter that feeds the
pure helper). Race-condition note in the docstring points back to the
migration header.
Integration test `list-title-flow.test.ts` (6 cases): admin add round-
trips into the catalog (LT-INT-01), Borja's member-attempt yields P0002
(LT-INT-02), the computeNextNumber math is end-to-end exercised against
the dev DB with 3 seeded "Compra #1/#2/#5" rows → 6 (LT-INT-03), the
no-matches path returns 1 (LT-INT-04), admin remove deletes the row
(LT-INT-05), and an empty-title insert is rejected with P0001 (LT-INT-06).
The pgTAP suite can't drive these because postgres bypasses
auth.uid — same caveat documented in Fase 15's common-items.test.ts.
Tests: 75 unit (was 56; +19), 185 integration (was 179; +6).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
