FN-6115: remove workflow lane chevron icon

Remove the workflow lane chevron while preserving collapse behavior.

- remove the chevron icon import and button contents from the workflow lane toggle
- keep the existing lane toggle button and accessible label behavior intact
- add a regression test that asserts the lane toggle renders without an svg icon

Files changed:
 packages/dashboard/app/components/Lane.tsx                | 5 +----
 packages/dashboard/app/components/__tests__/Lane.test.tsx | 7 +++++--
 2 files changed, 6 insertions(+), 6 deletions(-)

Fusion-Task-Id: FN-6115

Fusion-Task-Lineage: ce865f17-1e29-4345-b0cd-d5038ca56333

packages/dashboard/app/components/Lane.tsx

@@ -1,7 +1,6 @@
 import "./Lane.css";
 import { memo, useCallback, useEffect, useMemo, useRef } from "react";
 import { useTranslation } from "react-i18next";
-import { ChevronDown, ChevronRight } from "lucide-react";
 import type { Task, TaskDetail, Column as ColumnType, TaskCreateInput, GithubIssueAction } from "@fusion/core";
 import { Column } from "./Column";
 import { sortTasksForDisplayColumn } from "./taskSorting";
@@ -153,9 +152,7 @@ function LaneComponent(props: LaneProps) {
             ? t("lane.expand", "Expand {{name}} lane", { name: workflow.name })
             : t("lane.collapse", "Collapse {{name}} lane", { name: workflow.name })}
           data-testid={`lane-toggle-${workflow.id}`}
-        >
-          {collapsed ? <ChevronRight size={16} /> : <ChevronDown size={16} />}
-        </button>
+        />
         <h2 className="lane-name">{workflow.name}</h2>
         <span className="lane-count" data-testid={`lane-count-${workflow.id}`}>{tasks.length}</span>
       </div>

packages/dashboard/app/components/__tests__/Lane.test.tsx

@@ -24,9 +24,7 @@ vi.mock("../PluginSlot", () => ({ PluginSlot: () => null }));
 vi.mock("lucide-react", () => ({
   Link: () => null,
   Clock: () => null,
-  ChevronDown: () => null,
   ChevronUp: () => null,
-  ChevronRight: () => null,
   Archive: () => null,
   MoreVertical: () => null,
   AlertTriangle: () => null,
@@ -122,6 +120,11 @@ describe("Lane", () => {
     expect(props.onToggleCollapse).toHaveBeenCalledWith("builtin:coding");
   });
 
+  it("does not render a chevron icon in the lane toggle", () => {
+    render(<Lane {...baseProps()} />);
+    expect(screen.getByTestId("lane-toggle-builtin:coding").querySelector("svg")).toBeNull();
+  });
+
   it("shows the auto-merge toggle for human-review workflow columns", () => {
     render(<Lane {...baseProps()} autoMerge={false} onToggleAutoMerge={vi.fn()} />);
     expect(screen.getByText("Auto-merge")).toBeDefined();