feat: add a permission-gated UI action registry and action slots for plugins

Moves the terminal toolbar's hardwired AI button into a slot the ssh-terminal
plugin offers and the ai plugin fills, gated on ai.services.use.

src/ui/tests/lib/permissions.test.ts

@@ -0,0 +1,56 @@
+import { describe, expect, it } from "vitest";
+import { matchesPermission } from "@/lib/permissions";
+
+/**
+ * These cases mirror PermissionManager.hasPermission on the backend. If that
+ * changes, this file is the tripwire.
+ */
+describe("matchesPermission", () => {
+  it("grants on an exact match", () => {
+    expect(
+      matchesPermission(["ai.services.use"], false, "ai.services.use"),
+    ).toBe(true);
+  });
+
+  it("grants on the superuser wildcard", () => {
+    expect(matchesPermission(["*"], false, "anything.at.all")).toBe(true);
+  });
+
+  it("grants on each dotted wildcard level", () => {
+    expect(matchesPermission(["ai.services.*"], false, "ai.services.use")).toBe(
+      true,
+    );
+    expect(matchesPermission(["ai.*"], false, "ai.services.use")).toBe(true);
+  });
+
+  it("grants to an admin with no explicit permissions", () => {
+    expect(matchesPermission([], true, "ai.services.use")).toBe(true);
+  });
+
+  it("denies a non-admin without a matching grant", () => {
+    expect(matchesPermission([], false, "ai.services.use")).toBe(false);
+    expect(matchesPermission(["hosts.view"], false, "ai.services.use")).toBe(
+      false,
+    );
+  });
+
+  it("does not treat a prefix as a wildcard without the star", () => {
+    expect(matchesPermission(["ai.services"], false, "ai.services.use")).toBe(
+      false,
+    );
+  });
+
+  it("does not let a sibling wildcard grant an unrelated permission", () => {
+    expect(matchesPermission(["hosts.*"], false, "ai.services.use")).toBe(
+      false,
+    );
+  });
+
+  it("handles a single-segment permission", () => {
+    expect(matchesPermission(["admin"], false, "admin")).toBe(true);
+    // "admin.*" covers bare "admin" too: the backend builds the same
+    // single-segment wildcard, so the frontend must agree.
+    expect(matchesPermission(["admin.*"], false, "admin")).toBe(true);
+    expect(matchesPermission(["other"], false, "admin")).toBe(false);
+  });
+});