feat(store): read ledmatrix_min_version, aliases and commit from the registry (#686)

The store reads three optional registry fields: ledmatrix_min_version
(an incompatible install/update is refused before any download, with a
"Needs LEDMatrix X+" card badge), aliases (update/uninstall/reinstall by
registry id find a plugin installed under its manifest id, with registry
proof only), and commit (shown and linked on the store card). An older
plugins.json behaves as before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/SPORTS_UNIFICATION.md

@@ -514,8 +514,12 @@ a floor can be trusted against, and today it is not:
   the update path that re-downloads.
   `update_plugin`'s git branch pulls in place and re-downloads nothing, so it
   stayed ungated until `_gate_pulled_commit` closed it — checked after the pull
-  (the registry carries no floor field, so the incoming floor is unknowable
-  before it) and undone with `git reset --hard` to the pre-pull commit. That
+  (the registry then carried no floor field, so the incoming floor was
+  unknowable before it) and undone with `git reset --hard` to the pre-pull
+  commit. The registry now publishes `ledmatrix_min_version`, and install and
+  update refuse on it before downloading or pulling; both post-download gates
+  remain as the fallback for older registries, other branches and
+  `compatible_versions`. That
   route is rare in practice, since monorepo plugins install as archives; it was
   closed because the sunset rule in the plugins repo's
   `08-shared-sports-code.md` states as **condition 3** that the core enforces