feat(ui): /mouse toggle — enable terminal text selection/copy by default

Mouse-wheel tracking (xterm ?1000h) was always on so the wheel could scroll
the transcript, but it also captures mouse events, which prevents the
terminal's native text selection/drag-to-copy — a frequent ask.

Now mouse tracking defaults to OFF, so selecting/dragging output to copy
works out of the box. PageUp/PageDown still scroll (they always did). Toggle
the wheel back on with '/mouse on' (re-captures mouse events, so selection
won't work while on); '/mouse off' restores selection. '/mouse' shows the
current state. Documented in the /help list and README.

Verified: typecheck clean, build 257.55 KB, 263 tests pass.

README.md

@@ -115,6 +115,7 @@ Note: even models with genuine native tool-calling support occasionally emit a t
 /model <name>     switch the model used for the current backend
 /backend <name>   switch backend (ollama | lmstudio), keeps current model
 /mode <name>      view or force tool-call mode (native | fallback)
+  /mouse [on|off]   toggle mouse-wheel scroll (off by default so terminal text selection/copy works)
 /perm [mode]      cycle or set permission mode (default | plan | auto-edit | auto-accept)
 /status           show current model, backend, tool-call mode, and cwd
 /dashboard        show session stats: token I/O, elapsed/model time, turns, tool calls

src/ui/ink/App.tsx

@@ -136,6 +136,11 @@ export function App({
   const [inputValue, setInputValue] = useState("");
   const [permission, setPermission] = useState<PendingPermission | null>(null);
   const [exportPrompt, setExportPrompt] = useState<{ defaultName: string } | null>(null);
+  // Mouse-wheel tracking (xterm ?1000h) lets the wheel scroll the transcript, but it ALSO
+  // captures mouse events so the terminal can't select/drag text to copy it. Default off — copy/
+  // drag is more important than wheel scroll, and PageUp/PageDown already scroll. Toggle with
+  // `/mouse on|off`. When off the wheel does nothing in-app; the terminal's native selection works.
+  const [mouseMode, setMouseMode] = useState(false);
   const [streamingText, setStreamingText] = useState<string | null>(null);
   const [isThinking, setIsThinking] = useState(false);
   const [permMode, setPermMode] = useState<PermissionMode>("default");
@@ -275,13 +280,13 @@ export function App({
   // open would otherwise type them straight into the filename — simplest fix is to stop the
   // terminal from sending them at all rather than filtering inside a dependency we don't control.
   useEffect(() => {
-    if (!isRawModeSupported || phase !== "input" || exportPrompt) return;
+    if (!isRawModeSupported || phase !== "input" || exportPrompt || !mouseMode) return;
     stdout.write("[?1000h[?1006h");
     setRawMode(true);
     return () => {
       stdout.write("[?1006l[?1000l");
     };
-  }, [phase, isRawModeSupported, stdout, setRawMode, exportPrompt]);
+  }, [phase, isRawModeSupported, stdout, setRawMode, exportPrompt, mouseMode]);
 
   // A backgrounded bash job (see Ctrl+B below) can finish long after the turn that started it has
   // ended — this is how its completion still reaches the transcript.
@@ -985,6 +990,21 @@ export function App({
       }
       return;
     }
+    if (trimmed.startsWith("/mouse")) {
+      const arg = trimmed.slice("/mouse".length).trim().toLowerCase();
+      if (!arg) {
+        push({ kind: "notice", text: `Mouse wheel scroll: ${mouseMode ? "on" : "off"}. Use /mouse on|off.` });
+      } else if (arg === "on") {
+        setMouseMode(true);
+        push({ kind: "notice", text: "Mouse wheel scroll on (note: this captures mouse events, so terminal text selection/drag-to-copy won't work while on). Use /mouse off to copy text." });
+      } else if (arg === "off") {
+        setMouseMode(false);
+        push({ kind: "notice", text: "Mouse wheel scroll off — you can now select/drag terminal text to copy. Use PageUp/PageDown to scroll, or /mouse on to re-enable the wheel." });
+      } else {
+        push({ kind: "notice", text: `Unknown option "${arg}". Use /mouse on or /mouse off.`, isError: true });
+      }
+      return;
+    }
 
     // UserPromptSubmit hooks see the raw text before plugin-command expansion or @mention
     // resolution — a hook can block the message outright, or inject extra context (appended