Add Ctrl+Shift+C / Ctrl+Shift+V copy-paste in terminal panes

Uses attachCustomKeyEventHandler so xterm doesn't first consume Ctrl+V
and inject a raw ^V into the PTY. Paste routes through term.paste() so
broadcasting and bracketed paste continue to work.

src/components/XtermPane.tsx

@@ -169,6 +169,37 @@ export default function XtermPane({
         onInputRef.current?.(b64);
       });
 
+      // Ctrl+Shift+C / Ctrl+Shift+V — copy selection / paste from clipboard.
+      // Runs before xterm consumes the key, so the textarea never sees a raw
+      // Ctrl+V (which would otherwise inject ^V into the PTY). term.paste()
+      // routes through onData → writeToPane, so broadcasting and bracketed
+      // paste both keep working for free.
+      term?.attachCustomKeyEventHandler((e) => {
+        if (e.type !== "keydown") return true;
+        if (!e.ctrlKey || !e.shiftKey || e.altKey) return true;
+        if (e.code === "KeyC") {
+          const sel = term?.getSelection();
+          if (sel) {
+            void navigator.clipboard
+              .writeText(sel)
+              .catch((err) => console.warn("clipboard write failed:", err));
+          }
+          e.preventDefault();
+          return false;
+        }
+        if (e.code === "KeyV") {
+          e.preventDefault();
+          navigator.clipboard
+            .readText()
+            .then((text) => {
+              if (text && term) term.paste(text);
+            })
+            .catch((err) => console.warn("clipboard read failed:", err));
+          return false;
+        }
+        return true;
+      });
+
       // Focus detection: xterm.js doesn't expose onFocus as a first-class event
       // in all versions, so try the proposed API first then fall back to the DOM.
       term?.onSelectionChange(() => {}); // ensure addon system is initialised; noop