ci(labeler): fix dead rules, cover all plugin dirs, drop vendored artifacts (#121348)

* ci(labeler): fix dead rules and cover unlabeled plugin dirs

* chore: drop vendored swabble workflow and empty ActivityWidget asset catalog

test/scripts/labeler-extension-coverage.test.ts

@@ -0,0 +1,38 @@
+import { readdirSync, readFileSync } from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import { describe, expect, it } from "vitest";
+import { parse } from "yaml";
+
+type LabelerRule = Array<{
+  "changed-files"?: Array<{
+    "any-glob-to-any-file"?: string[];
+  }>;
+}>;
+
+const repoRoot = path.resolve(fileURLToPath(new URL("../..", import.meta.url)));
+const extensionsRoot = path.join(repoRoot, "extensions");
+const labelerPath = path.join(repoRoot, ".github/labeler.yml");
+
+const extensionDirectories = readdirSync(extensionsRoot, { withFileTypes: true })
+  .filter((entry) => entry.isDirectory())
+  .map((entry) => entry.name)
+  .sort();
+const extensionDirectorySet = new Set(extensionDirectories);
+const labeler = parse(readFileSync(labelerPath, "utf8")) as Record<string, LabelerRule>;
+const extensionGlobDirectories = Object.values(labeler)
+  .flatMap((rules) => rules)
+  .flatMap((rule) => rule["changed-files"] ?? [])
+  .flatMap((changedFiles) => changedFiles["any-glob-to-any-file"] ?? [])
+  .flatMap((glob) => glob.match(/^extensions\/([^/]+)\//)?.[1] ?? []);
+const coveredExtensionDirectories = new Set(extensionGlobDirectories);
+
+describe("labeler extension coverage", () => {
+  it("covers every extension directory", () => {
+    expect(extensionDirectories.filter((dir) => !coveredExtensionDirectories.has(dir))).toEqual([]);
+  });
+
+  it("references only existing extension directories", () => {
+    expect(extensionGlobDirectories.filter((dir) => !extensionDirectorySet.has(dir))).toEqual([]);
+  });
+});