feat(web): tap-to-copy button on every chat message

Each user and assistant message gets a copy button (⧉ → ✓) that puts the whole
message on the clipboard. Assistant copies the raw markdown (its dataset.raw);
user copies its text.

- copyToClipboard uses the async Clipboard API when available and falls back to a
  hidden-textarea + execCommand with an explicit iOS selection range, so it works
  on the iPhone PWA over plain-HTTP LAN (no secure context).
- Copy sits in the assistant rate-bar and in a right-aligned bar on user bubbles;
  tools stay visible on touch (@media hover:none) since there's no hover on iOS.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lyra/web/static/index.html

@@ -473,6 +473,7 @@
 	  up.addEventListener("click", () => rateMessage(div, 1, up, down));
 	  down.addEventListener("click", () => rateMessage(div, -1, up, down));
 	  bar.appendChild(up); bar.appendChild(down);
+	  bar.appendChild(makeCopyBtn(() => div.dataset.raw || div.textContent || ""));
 	  div.appendChild(bar);
 	}
 
@@ -491,6 +492,62 @@
 	  down.classList.toggle("rated", value === -1);
 	}
 
+	// Copy text to the clipboard. Uses the async Clipboard API when available
+	// (HTTPS / localhost), and falls back to a hidden-textarea + execCommand for
+	// iOS over plain-HTTP LAN (where navigator.clipboard is undefined).
+	function copyToClipboard(text) {
+	  text = text == null ? "" : String(text);
+	  if (navigator.clipboard && navigator.clipboard.writeText) {
+	    return navigator.clipboard.writeText(text).catch(() => legacyCopy(text));
+	  }
+	  return legacyCopy(text);
+	}
+	function legacyCopy(text) {
+	  return new Promise((resolve, reject) => {
+	    const ta = document.createElement("textarea");
+	    ta.value = text;
+	    ta.contentEditable = "true";
+	    ta.readOnly = false;
+	    ta.style.position = "fixed";
+	    ta.style.top = "0";
+	    ta.style.left = "0";
+	    ta.style.opacity = "0";
+	    document.body.appendChild(ta);
+	    const range = document.createRange();
+	    range.selectNodeContents(ta);
+	    const sel = window.getSelection();
+	    sel.removeAllRanges();
+	    sel.addRange(range);
+	    ta.setSelectionRange(0, text.length);  // iOS needs an explicit range
+	    let ok = false;
+	    try { ok = document.execCommand("copy"); } catch (e) { ok = false; }
+	    sel.removeAllRanges();
+	    document.body.removeChild(ta);
+	    ok ? resolve() : reject(new Error("copy failed"));
+	  });
+	}
+	// A small per-message copy button. getText is read at click time.
+	function makeCopyBtn(getText) {
+	  const b = document.createElement("button");
+	  b.className = "copy-btn";
+	  b.type = "button";
+	  b.textContent = "⧉";
+	  b.title = "Copy message";
+	  b.addEventListener("click", (e) => {
+	    e.stopPropagation();
+	    copyToClipboard(typeof getText === "function" ? getText() : getText)
+	      .then(() => {
+	        b.textContent = "✓"; b.classList.add("copied");
+	        setTimeout(() => { b.textContent = "⧉"; b.classList.remove("copied"); }, 1200);
+	      })
+	      .catch(() => {
+	        b.textContent = "✗";
+	        setTimeout(() => { b.textContent = "⧉"; }, 1200);
+	      });
+	  });
+	  return b;
+	}
+
 	function addMessage(role, text, autoScroll = true) {
 	  const messagesEl = document.getElementById("messages");
 
@@ -502,6 +559,12 @@
 	    addRateBar(msgDiv);
 	  } else {
 	    msgDiv.textContent = text;
+	    if (role === "user") {
+	      const bar = document.createElement("div");
+	      bar.className = "rate-bar";
+	      bar.appendChild(makeCopyBtn(() => text));
+	      msgDiv.appendChild(bar);
+	    }
 	  }
 	  messagesEl.appendChild(msgDiv);