Only report a missing plugin web build when one is expected (#1013)

Plugins with only host, instance or ctl code have no reason to ship a
webpack build, yet the plugin list showed "Missing dist/web/manifest.json"
as an error for them and the controller logged a warning on every start.

Decide whether a build is expected from the plugin declaration, using the
same rule the create tool uses to decide when to generate one: a web or
controller entrypoint, or any config fields. Plugins outside that rule get
no bundle path and no error, the web UI skips loading them, and the plugin
pages show them as having no web module instead of an error or a prompt to
reload.

Fixes #1004

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

test/controller/routes.js

@@ -102,7 +102,7 @@ describe("controller/src/routes", function() {
 		});
 		it("should report missing manifest and entrypoint", async function() {
 			controller.pluginInfos = [
-				{ name: "foo", version: "1.0.0", npmPackage: "foo" },
+				{ name: "foo", version: "1.0.0", npmPackage: "foo", webEntrypoint: "dist/web/index.js" },
 				{ name: "bar", version: "1.0.0", npmPackage: "bar", manifest: {} },
 				{ name: "baz", version: "1.0.0", npmPackage: "baz", manifest: { "baz.js": "remoteEntry.js" } },
 			];
@@ -115,6 +115,19 @@ describe("controller/src/routes", function() {
 			assert.equal(data[1].loaded, false);
 			assert.equal(data[1].enabled, false);
 		});
+		it("should not report a missing manifest for plugins without a web build", async function() {
+			controller.pluginInfos = [
+				{ name: "foo", version: "1.0.0", npmPackage: "foo", hostEntrypoint: "dist/node/host.js" },
+				{ name: "bar", version: "1.0.0", npmPackage: "bar", controllerEntrypoint: "dist/node/controller.js" },
+				{ name: "baz", version: "1.0.0", npmPackage: "baz", instanceConfigFields: {} },
+			];
+			let response = await fetch(endpoint);
+			assert.equal(response.status, 200);
+			let data = await response.json();
+			assert.deepEqual(data[0].web, {});
+			assert.equal(data[1].web.error, "Missing dist/web/manifest.json");
+			assert.equal(data[2].web.error, "Missing dist/web/manifest.json");
+		});
 	});
 	describe("/api/cluster-name", function() {
 		let endpoint;