Change message copy button to copy content instead of anchor link

The per-message copy button previously copied a URL with a hash
anchor (#msg-{uuid}) for deep linking. Replace this with copying
the actual message content: for tool_call messages it copies the
tool name and input; for all other categories it copies the text
body. This is more immediately useful — users copying message
content is far more common than sharing anchor links.

Button title updated from "Copy link to message" to "Copy message
content" to match the new behavior.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/client/components/MessageBubble.tsx

@@ -153,14 +153,16 @@ export function MessageBubble({
           <button
             onClick={(e) => {
               e.stopPropagation();
-              const url = `${window.location.origin}${window.location.pathname}#msg-${message.uuid}`;
-              navigator.clipboard.writeText(url).then(() => {
+              const text = message.category === "tool_call"
+                ? `${message.toolName || "Tool Call"}\n${message.toolInput || ""}`
+                : message.content;
+              navigator.clipboard.writeText(text).then(() => {
                 setLinkCopied(true);
                 setTimeout(() => setLinkCopied(false), 1500);
               }).catch(() => {});
             }}
             className="flex items-center justify-center w-7 h-7 rounded-md text-foreground-muted hover:text-foreground hover:bg-surface-overlay/60 transition-colors"
-            title="Copy link to message"
+            title="Copy message content"
           >
             {linkCopied ? (
               <svg className="w-4 h-4 text-green-400" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>