docs: list the Edge Add-ons build alongside the Chrome Web Store

The extension is now published to Edge Add-ons, but every install path
still pointed Edge users at the Chrome Web Store. Both READMEs and
AGENT_INSTALL.md now name a store per browser, and `bsk doctor` offers
both listings when no browser is connected.

Two Edge-specific gaps went with it: Edge blocks content-script injection
on its own storefront the same way Chrome does, so the borrow-confirmation
overlay must treat microsoftedge.microsoft.com/addons as non-injectable;
and the Chinese README still described the pre-install.ps1 manual Windows
setup.

Also give the DeepSeek Harness section its npm package link and the
profile-start step, so plugin users have a complete path.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/extension/src/tools/__tests__/borrow-confirmation.test.ts

@@ -612,4 +612,14 @@ describe("isInjectableContentScriptUrl", () => {
     ).toBe(false);
     expect(isInjectableContentScriptUrl("https://chromewebstore.google.com/")).toBe(false);
   });
+
+  it("rejects the Edge Add-ons store", () => {
+    expect(
+      isInjectableContentScriptUrl(
+        "https://microsoftedge.microsoft.com/addons/detail/browserskill/emacgiaaaiojkkpkddmmdfhmokgmnikg",
+      ),
+    ).toBe(false);
+    // Non-store paths on the same host stay injectable.
+    expect(isInjectableContentScriptUrl("https://microsoftedge.microsoft.com/")).toBe(true);
+  });
 });