fix(ui): stop stamping a dead blur class on chat links containing 'tail' (#123154)

The DOMPurify afterSanitizeAttributes hook added class
chat-link-tail-blur to every rendered chat link whose href merely
contains the substring "tail" (docs.openclaw.ai/tailscale, /details/,
retail, ...). No stylesheet or script anywhere consumes the class: it is
an orphaned producer that survived the Control UI import, polluting
sanitized HTML and the markdown LRU cache, and priming a foot-gun where
any future .chat-link-tail-blur CSS rule would visually blur docs links
in every transcript.

Link presentation classes are owned by markdown-parser.ts
(web-link-classes, hostname-based); delete the substring classifier.

ui/src/components/markdown.test.ts

@@ -50,6 +50,15 @@ describe("toSanitizedMarkdownHtml", () => {
     );
   });
 
+  it("does not stamp presentation classes on links whose href contains 'tail'", () => {
+    const fragment = htmlFragment(
+      toSanitizedMarkdownHtml("[tailscale docs](https://docs.openclaw.ai/tailscale)"),
+    );
+    const link = fragment.querySelector("a");
+    expect(link?.getAttribute("href")).toBe("https://docs.openclaw.ai/tailscale");
+    expect(link?.classList.contains("chat-link-tail-blur")).toBe(false);
+  });
+
   it("strips unsupported citation control markers before display", () => {
     const html = toSanitizedMarkdownHtml(
       "v2026.5.20 release note citeturn2view0\n\nStill readable.",

ui/src/components/markdown.ts

@@ -1,4 +1,3 @@
-import { normalizeLowercaseStringOrEmpty } from "@openclaw/normalization-core/string-coerce";
 // Control UI module implements markdown behavior.
 import DOMPurify from "dompurify";
 import { stripUnsupportedCitationControlMarkers } from "../../../src/shared/text/citation-control-markers.js";
@@ -318,7 +317,6 @@ const APP_RESOURCE_PATH_PREFIXES = [
   ["plugins", "diffs-language-pack"],
 ];
 const markdownCache = new Map<string, string>();
-const TAIL_LINK_BLUR_CLASS = "chat-link-tail-blur";
 
 function getCachedMarkdown(key: string): string | null {
   const cached = markdownCache.get(key);
@@ -469,9 +467,6 @@ function installHooks() {
 
     node.setAttribute("rel", "noreferrer noopener");
     node.setAttribute("target", "_blank");
-    if (normalizeLowercaseStringOrEmpty(href).includes("tail")) {
-      node.classList.add(TAIL_LINK_BLUR_CLASS);
-    }
   });
 }