feat(admin): per-feed Subscribe chips with copy/open/validate for RSS/Atom/JSON

Replace the stacked RSS/Atom URL rows in the dashboard with a compact
"Subscribe" chip block exposing all three feed formats — including JSON
Feed, previously absent from the admin UI. Each chip carries copy, open,
and validate actions; validation links to the W3C Feed Validator (RSS/Atom)
and validator.jsonfeed.org (JSON). The Table view's RSS+Atom columns fold
into a single Formats column.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/infrastructure/urls.test.ts

@@ -0,0 +1,58 @@
+import { describe, it, expect } from "vitest";
+import {
+  feedRssUrl,
+  feedAtomUrl,
+  feedJsonUrl,
+  feedFormatUrl,
+  feedValidatorUrl,
+} from "./urls";
+import { Env } from "../types";
+
+const env = { DOMAIN: "getmynews.app" } as Env;
+const feedId = "gAf6wiKyanpppcKX9o3B_Q";
+
+describe("feed URL builders", () => {
+  it("builds RSS/Atom/JSON feed URLs", () => {
+    expect(feedRssUrl(feedId, env)).toBe(
+      "https://getmynews.app/rss/gAf6wiKyanpppcKX9o3B_Q",
+    );
+    expect(feedAtomUrl(feedId, env)).toBe(
+      "https://getmynews.app/atom/gAf6wiKyanpppcKX9o3B_Q",
+    );
+    expect(feedJsonUrl(feedId, env)).toBe(
+      "https://getmynews.app/json/gAf6wiKyanpppcKX9o3B_Q",
+    );
+  });
+
+  it("resolves a format to its feed URL", () => {
+    expect(feedFormatUrl("rss", feedId, env)).toBe(feedRssUrl(feedId, env));
+    expect(feedFormatUrl("atom", feedId, env)).toBe(feedAtomUrl(feedId, env));
+    expect(feedFormatUrl("json", feedId, env)).toBe(feedJsonUrl(feedId, env));
+  });
+});
+
+describe("feedValidatorUrl", () => {
+  it("points JSON feeds at validator.jsonfeed.org with the encoded feed URL", () => {
+    expect(feedValidatorUrl("json", feedId, env)).toBe(
+      "https://validator.jsonfeed.org/?url=" +
+        encodeURIComponent(feedJsonUrl(feedId, env)),
+    );
+  });
+
+  it("points RSS and Atom feeds at the W3C feed validator", () => {
+    expect(feedValidatorUrl("rss", feedId, env)).toBe(
+      "https://validator.w3.org/feed/check.cgi?url=" +
+        encodeURIComponent(feedRssUrl(feedId, env)),
+    );
+    expect(feedValidatorUrl("atom", feedId, env)).toBe(
+      "https://validator.w3.org/feed/check.cgi?url=" +
+        encodeURIComponent(feedAtomUrl(feedId, env)),
+    );
+  });
+
+  it("percent-encodes the feed URL so the validator query is well-formed", () => {
+    const url = feedValidatorUrl("json", feedId, env);
+    expect(url).toContain("https%3A%2F%2Fgetmynews.app%2Fjson%2F");
+    expect(url).not.toContain("?url=https://");
+  });
+});