fix(store): gate the git-pull update path

`install_plugin` gates every route that re-downloads, `_reinstall_with_rollback`
included. `update_plugin` has one branch that re-downloads nothing: a git
checkout pulls in place, installs dependencies, and returns True. A pull could
therefore deliver a manifest flooring above this core and nothing would notice
until the plugin failed to load — which surfaces as one line in the journal and
a display that silently stopped appearing.

Checked after the pull rather than before it, for the same reason
`_install_plugin_impl` checks after the download: the registry carries no
compatibility field, so the incoming floor is only knowable once the new commit
is on disk.

Undone with `git reset --hard` to the pre-pull commit rather than by removing
the directory. This is a live checkout, the old commit is still in the object
store, and the reset leaves the user on the exact version they were already
running — the same promise `_reinstall_with_rollback` makes, reached by the
means this path actually has, with no window where the plugin directory does
not exist. An unreadable manifest allows: it is not evidence of a floor.

Scope, stated plainly: monorepo plugins install as archives and update through
`_reinstall_with_rollback`, so they were already gated. Only registry entries
with no `plugin_path` reach this branch. It is closed anyway because the sunset
rule in the plugins repo's `08-shared-sports-code.md` names, as condition 3,
that the core enforces the floor "at install/update time" — and B6 rests on
that being true rather than merely written down. `install_from_url` is still
ungated; the tests say so rather than letting the next reader assume otherwise.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014RRtqXDCnvnY6EQwhT5CV9

docs/SPORTS_UNIFICATION.md

@@ -27,7 +27,7 @@ These are independent concerns. Conflating them is what produces god classes.
 | Plugin loads on a core that predates a module | Guarded import with a bundled fallback (`try: from src.X import Y / except ModuleNotFoundError: from y import Y`) |
 | Plugin loads on a core that predates a *method* | Capability probing — `hasattr(SportsCore, "_detect_stale_games")` — never a version comparison. The loader's compat check is advisory-only (it logs and continues), so probing is the real protection. |
 | Core changes never break a plugin's rendering | The **view-model contract**: `_extract_game_details_common` returns a dict whose `GUARANTEED_KEYS` are frozen by `test/test_skin_system.py::TestViewModelContract`. Keys may be added, never renamed or removed. |
-| A plugin can drop its bundled copy safely | The **sunset rule**: its manifest must floor `ledmatrix_min_version` at the first core release shipping the module (recorded in `CHANGELOG.md`) — *necessary but not sufficient*. Nothing enforces that floor today, so the copy also waits for the B6 gate below. |
+| A plugin can drop its bundled copy safely | The **sunset rule**: its manifest must floor `ledmatrix_min_version` at the first core release shipping the module (recorded in `CHANGELOG.md`) — *necessary but not sufficient*. The store enforces that floor on every route that installs or updates, but a floor cannot reach a user who never updates, so the copy also waits for the B6 gate below. |
 
 The core API is **additive-only**. A method the plugins call is never removed or
 given a new required parameter; new behavior arrives as new methods with
@@ -234,6 +234,19 @@ a floor can be trusted against, and today it is not:
   compares the plugin's manifest version against the registry's
   `latest_version` and nothing else.
 
+  *Fixed, in two parts.* `install_plugin` gained the gate in #431/#433, which
+  covers every route that re-downloads, `_reinstall_with_rollback` included.
+  `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
+  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
+  the floor "at install/update time", and B6 rests on that being true rather
+  than merely written down. `install_from_url` — sideloading a plugin from a
+  URL — is still ungated.
+
 So B4 is: tag and release 3.2.0; make the tag, the release, and `__version__`
 agree, and keep them agreeing; reconsider the `< 2.0.0` skip; migrate manifests
 from `ledmatrix_min` to `ledmatrix_min_version`; and add the install/update