fix(terminal): touchpad scrolls 1:1 with the finger

xterm.js sends one wheel report per event whatever its size and damps a
touchpad's pixel deltas x0.3, so a swipe crawled. With mouse tracking on,
TerminalView now sends the SGR reports itself (lib/wheelReports.ts): one
per 5 rows of travel (what one report scrolls in a Claude pane), the
remainder carried between events, at least one per wheel notch, at the
pointer's cell with xterm's modifier bits.

client/src/components/run/TerminalView.tsx

@@ -86,6 +86,7 @@ import {
   sameFilesHere,
 } from "../../lib/promptAttach";
 import { attachImeInput } from "../../lib/imeInput";
+import { wheelReports, type WheelState } from "../../lib/wheelReports";
 import { nativePasteKey, nativePasteWorks, readNativePaste } from "../../lib/nativePaste";
 import { usePermissions } from "../AuthGate";
 import { TERMINAL_FONTS, readTerminalFont } from "../../lib/terminalFont";
@@ -524,9 +525,32 @@ export const TerminalView = memo(function TerminalView({
       // wheel report itself — psmux scrolls, or hands it to the pane's app.
       // ponytail: at 1;1, which is all psmux reports to the app anyway.
       let ownWheel = false;
+      // Tracked: the reports are this pane's own too — one per
+      // LINES_PER_REPORT rows of travel (lib/wheelReports.ts), where xterm
+      // sends one per event and damps a touchpad ×0.3. SGR, as tmux always
+      // asks for it; at the pointer's cell, with xterm's modifier bits.
+      const wheelState: WheelState = { partial: 0 };
+      const sendWheel = (ev: WheelEvent) => {
+        const screen = term.element?.querySelector(".xterm-screen");
+        const box = screen?.getBoundingClientRect();
+        if (!box || !box.height || !box.width) return;
+        const n = wheelReports(wheelState, ev, box.height / term.rows, term.rows);
+        const ws = wsRef.current;
+        if (!n || !ws || ws.readyState !== WebSocket.OPEN) return;
+        const clamp = (v: number, max: number) => Math.min(max, Math.max(1, v));
+        const col = clamp(Math.floor(((ev.clientX - box.left) / box.width) * term.cols) + 1, term.cols);
+        const row = clamp(Math.floor(((ev.clientY - box.top) / box.height) * term.rows) + 1, term.rows);
+        const button = (n < 0 ? 64 : 65) | (ev.altKey ? 8 : 0) | (ev.ctrlKey ? 16 : 0);
+        ws.send(`\x1b[<${button};${col};${row}M`.repeat(Math.abs(n)));
+      };
       term.attachCustomWheelEventHandler((ev) => {
         const mode = term.modes.mouseTrackingMode;
         const tracked = mode !== "none" && mode !== "x10";
+        // Shift+wheel stays xterm's (it reports nothing for it).
+        if (tracked && !ev.shiftKey) {
+          sendWheel(ev);
+          return false;
+        }
         if (!tracked && ownWheel) {
           if (ev.deltaY && wsRef.current?.readyState === WebSocket.OPEN) {
             wsRef.current.send(`\x1b[<${ev.deltaY < 0 ? 64 : 65};1;1M`);

client/src/components/run/__tests__/TerminalView.test.tsx

@@ -21,6 +21,7 @@ import {
   screen,
   waitFor,
 } from "@testing-library/react";
+import { Terminal } from "@xterm/xterm";
 import { TerminalView, altArrowSeq, loadXterm } from "../TerminalView";
 import { pasteToLane, pasteToRun } from "../../../lib/panePaste";
 import { __resetNativePaste, nativePasteWorks } from "../../../lib/nativePaste";
@@ -326,13 +327,33 @@ describe("TerminalView", () => {
     expect(wheelHandlerMock.mock.calls[0]![0]!(new Event("wheel"))).toBe(false);
   });
 
-  it("lets the wheel through once the pane's program tracks the mouse", () => {
-    // tmux with `mouse on` sets this; the wheel must reach it as a real SGR
-    // report, so returning false here would kill scrolling entirely.
+  /** Gives the mocked terminal an on-screen box: 10px per column and per row. */
+  const screenBox = () => {
+    const term = vi.mocked(Terminal).mock.results[vi.mocked(Terminal).mock.results.length - 1]!.value as { element: HTMLElement };
+    const screen = document.createElement("div");
+    screen.className = "xterm-screen";
+    screen.getBoundingClientRect = () =>
+      ({ left: 0, top: 0, width: termState.cols * 10, height: termState.rows * 10 }) as DOMRect;
+    term.element.appendChild(screen);
+  };
+
+  it("sends a tracked wheel itself, one report per LINES_PER_REPORT rows, at the pointer", () => {
+    // tmux with `mouse on` sets this. xterm would send ONE report per event and
+    // damp a touchpad ×0.3 — a swipe crawled — so the pane sends its own.
     termState.modes.mouseTrackingMode = "any";
     termState.buffer.active.type = "alternate";
     render(<TerminalView runId="agenthub-lane-1" wsBaseUrl="ws://localhost:4820" />);
-    expect(wheelHandlerMock.mock.calls[0]![0]!(new Event("wheel"))).toBe(true);
+    screenBox();
+    const ws = MockWebSocket.instances[MockWebSocket.instances.length - 1]!;
+    ws.sent.length = 0;
+    const wheel = wheelHandlerMock.mock.calls[0]![0]!;
+    // A notch of 6 rows: one report, at the cell under the pointer.
+    expect(wheel(new WheelEvent("wheel", { deltaY: -60, clientX: 45, clientY: 72 }))).toBe(false);
+    expect(ws.sent).toEqual(["\x1b[<64;5;8M"]);
+    // A touchpad: 4 steps of 25px = 10 rows = two reports, sent as they add up.
+    ws.sent.length = 0;
+    for (let i = 0; i < 4; i++) wheel(new WheelEvent("wheel", { deltaY: 25, clientX: 5, clientY: 5 }));
+    expect(ws.sent.join("")).toBe("\x1b[<65;1;1M".repeat(2));
   });
 
   it("lets the wheel through on a normal buffer, where xterm scrolls scrollback", () => {
@@ -361,10 +382,11 @@ describe("TerminalView", () => {
     expect(wheel(new WheelEvent("wheel", { deltaY: -100 }))).toBe(false);
     expect(wheel(new WheelEvent("wheel", { deltaY: 100 }))).toBe(false);
     expect(ws.sent).toEqual(["\x1b[<64;1;1M", "\x1b[<65;1;1M"]);
-    // Tracked again (a tmux that does report): xterm sends it, never twice.
+    // Tracked again (a tmux that does report): sent once, by the tracked path.
     termState.modes.mouseTrackingMode = "any";
-    expect(wheel(new WheelEvent("wheel", { deltaY: -100 }))).toBe(true);
-    expect(ws.sent).toHaveLength(2);
+    screenBox();
+    expect(wheel(new WheelEvent("wheel", { deltaY: -100 }))).toBe(false);
+    expect(ws.sent).toHaveLength(3);
   });
 
   it("keeps Shift+Tab in the terminal instead of letting focus escape", () => {