chore: import upstream snapshot with attribution

extension/platform/plugin.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package platform
+
+// Plugin is the single contract a third-party / embedding integrator
+// implements to extend lark-cli. Four methods, every one mandatory.
+//
+// Name must match the grammar ^[a-z0-9][a-z0-9-]*$. The "." character
+// is forbidden so plugin-name + hookName namespacing never produces
+// ambiguous joins.
+//
+// Capabilities must be implemented even when every field is zero. The
+// requirement is deliberate: it keeps FailurePolicy / Restricts in the
+// author's eyeline.
+//
+// Install runs once during the Bootstrap pipeline. The plugin uses the
+// supplied Registrar to register hooks and (optionally) a Rule. Errors
+// returned from Install honour the plugin's Capabilities.FailurePolicy
+// (fail-open warns + skips this plugin; fail-closed aborts the CLI).
+type Plugin interface {
+	Name() string
+	Version() string
+	Capabilities() Capabilities
+	Install(r Registrar) error
+}