feat: serve games from bundles through /data

A registry scans the bundles directory -- ATLAS_BUNDLES_DIR in
development, the application data directory otherwise -- opens every
.atlas it finds, lets the newest bundle of each game win, and composes
the catalog the frontend boots from. Each rescan builds an immutable
snapshot and swaps it in whole, so a request sees one consistent world
and bundles retired by a swap close only after anything reading them
has finished.

Content is served under /data/g/<game>/<stamp>/, the stamp taken from
the bundle's own version: every URL names exactly one build of one
game, so tiles, payloads and icons are cached as immutable and a
replaced bundle simply arrives at new URLs. The composed catalog is
never cached at all. The framework's /static/ mount still serves the
shell, which stays embedded.

The frontend now reads the composed catalog, addresses everything
through each game's stamped base, keys maps by slug rather than by the
numeric identity the old tree was filed under, and takes its tile grid
from the game rather than from a catalog-wide constant -- bundles from
different sources need not agree on one. The engine is built when the
first game is chosen, since its world is sized from that game's grid.

The embed-reading tests give way to two suites: routes exercised over
fixture bundles built by the writer itself, and the corpus invariants
-- pin counts, tile completeness, icon presence, the Los Santos
projection -- reread from dist/bundles when the bundles have been
built, skipped when they have not.

commit

4009da39fbcc9ed052bf8e26c2c513da6494601f

parent

f67dc268e2d8da6b882483c6e832036cbbce1c1c

author

Dami <dami.etoile@gmail.com>