The full-bleed 4-poster collage drowned the on-tile text. Split PosterTile in two: the top
half shows up to 2 montage posters, the bottom half is a solid colour-hash band that carries
the label, so the text is always readable. Genre tiles drop the count (just the label now);
collection tiles show the name on one truncated line plus a sub-line of item count · total
runtime. A group with no art falls back to an all-colour tile.
Backend: `/collections` cards gain `total_runtime_s` (a new `runtime_by_key` grouped sum) and
their montage art is capped at 2. Frontend: PosterTile reworked; a `collectionMeta` helper
builds the count·runtime sub-line via the existing formatRuntime.
Verified live: collection and genre tiles render 2 posters over a readable colour band with
the right sub-lines; colour fallback intact for art-less groups.
Gate: tsc/lint/knip/prettier clean, 423 vitest; backend ruff clean, collections tests green
(+ a new art/runtime assertion).
peter
37d11b602f