feat: introduce device plugin runtime boundary

packages/plugin-sdk/README.md

@@ -1,11 +1,16 @@
 # Mission Core Plugin SDK
 
-This directory reserves the versioned host/plugin contract. It is not yet a
-published SDK and must not be treated as an implemented runtime.
+This directory owns the versioned host/plugin contract. The v1alpha frontend
+contract, validated registry, generic runtime envelope, and backend read-only
+catalog are implemented in-tree, but this is not yet a separately published
+SDK package.
 
-The first contract will define:
+The v1alpha1 contract currently validates one model per plugin, one reviewed
+`transitional-in-process` backend entrypoint, a required safe `state.read`
+action, and declared UI/action metadata. It establishes:
 
-- plugin manifest, version compatibility, firmware profiles, and permissions;
+- plugin manifest, version compatibility, firmware profiles, and declarative
+  permissions;
 - discovery candidates and opaque device references;
 - provisioning requests using secret references;
 - device-session lifecycle and health;
@@ -14,5 +19,25 @@ The first contract will define:
 - SceneSink and event interfaces;
 - capability-driven UI contribution data without plugin-owned layout.
 
-The XGRIDS K1 extraction is the first acceptance test. A synthetic reference
-plugin will verify that no K1 names or protocol assumptions remain in core.
+The XGRIDS K1 extraction is the first real-device acceptance path. Synthetic
+multi-plugin composition tests verify that backend routing has no K1 identity or
+protocol assumption; static boundary tests enforce the same rule in the frontend.
+
+Current implementation references:
+
+- `apps/control-station/src/core/device-plugins/` — TypeScript manifest and UI
+  contribution contracts;
+- `apps/control-station/src/core/runtime/` — normalized runtime envelope;
+- `src/k1link/web/plugin_catalog.py` — strict backend manifest validation;
+- `src/k1link/web/plugin_runtime.py` — host-owned allowlisted action dispatcher;
+- `src/k1link/web/device_plugin_composition.py` — manifest factory loader and
+  startup parity check between catalog and executable adapters;
+- `docs/adr/0003-device-plugin-ui-and-runtime-boundary.md` — accepted boundary
+  and extraction sequence.
+
+The v1alpha lifecycle is fail-closed: inactive provider shells must perform no
+I/O, events are scoped by plugin ID, and selection cannot change until the
+active plugin confirms teardown. Process isolation and independent device
+session IDs remain the next SDK milestone. `permissions`, `mutating`, and
+`secretFields` are contract metadata only in v1alpha1; host authorization and
+secret-vault enforcement are not implemented yet.