fix(run,lanes): prompt autocomplete, per-lane Active runs, compact Changes header

- The run form's prompt box offers suggestions again: `/` lists the run
  cwd's project and user commands and skills plus the CLI built-ins
  (claude lanes only), `@` lists files under the cwd; Enter picks while
  the list is open and sends otherwise. The 2f39f4e rewrite had left a
  bare textarea that ignored both.
- Active runs lists only the current lane's runs and external sessions
  (sessions matched to the lane by longest path-boundary cwd), instead of
  every lane's.
- The Changes panel's git line and its actions are one compact row in one
  card, and the mode/range toolbar is one wrapping row.
- The lane card hides itself when it has nothing to show, instead of
  leaving an empty frame where the git row used to be.

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

@@ -17,6 +17,7 @@ import { beforeEach, describe, expect, it, vi } from "vitest";
 import i18n from "i18next";
 import { RunSetup } from "../RunSetup";
 import type { CwdSuggestion } from "../../../lib/api";
+import { api } from "../../../lib/api";
 
 vi.mock("../../../lib/api", async (importOriginal) => {
   const actual = await importOriginal<Record<string, unknown>>();
@@ -26,7 +27,22 @@ vi.mock("../../../lib/api", async (importOriginal) => {
     api: {
       run: { files: r({ items: [] }) },
       sessions: { list: r({ sessions: [], total: 0, limit: 100, offset: 0 }) },
-      ccConfig: { file: r({ text: "" }) },
+      ccConfig: {
+        file: r({ text: "" }),
+        commands: r({
+          items: [
+            {
+              scope: "project",
+              name: "ship-it",
+              frontmatter: { description: "Ship the change" },
+              preview: "",
+            },
+          ],
+        }),
+        skills: r({
+          items: [{ scope: "user", name: "review-pr", frontmatter: {}, preview: "Review a PR" }],
+        }),
+      },
     },
   };
 });
@@ -66,7 +82,6 @@ function renderSetup(overrides: Partial<React.ComponentProps<typeof RunSetup>> =
         busy={false}
         activeRuns={null}
         resumeSession={null}
-        slashCommands={[]}
         runHistory={[]}
         tool="claude"
         sandbox="workspace-write"
@@ -300,7 +315,6 @@ describe("RunSetup — resume picker scopes sessions to the selected lane", () =
           busy={false}
           activeRuns={null}
           resumeSession={null}
-          slashCommands={[]}
           runHistory={[]}
           laneCwd="/Users/tester/lane-b"
           tool="claude"
@@ -364,3 +378,48 @@ describe("RunSetup — per-tool fields", () => {
     expect(onResumeLast).toHaveBeenCalled();
   });
 });
+
+describe("RunSetup — / and @ suggestions in the prompt box", () => {
+  const box = () => screen.getByPlaceholderText(i18n.t("run:fields.promptPlaceholderTerminal"));
+
+  it("lists the lane's commands, skills and the CLI built-ins on /, and Enter picks one", async () => {
+    const { spies } = renderSetup({ prompt: "" });
+    fireEvent.change(box(), { target: { value: "/rev" } });
+
+    // Both prefix matches; the shorter name ranks first.
+    const options = await screen.findAllByRole("option");
+    expect(options.map((o) => o.textContent)).toEqual([
+      expect.stringContaining("/review"),
+      expect.stringContaining("/review-pr"),
+    ]);
+    fireEvent.keyDown(box(), { key: "ArrowDown" });
+    // Read for the directory the run will start in, not the server's own.
+    expect(api.ccConfig.commands).toHaveBeenCalledWith(undefined, "/Users/tester");
+    expect(api.ccConfig.skills).toHaveBeenCalledWith(undefined, "/Users/tester");
+
+    fireEvent.keyDown(box(), { key: "Enter" });
+    expect(spies.onPromptChange).toHaveBeenLastCalledWith("/review-pr ");
+    // Enter picked the suggestion; it did not send the prompt.
+    expect(spies.onStart).not.toHaveBeenCalled();
+  });
+
+  it("suggests files under the cwd on @", async () => {
+    vi.mocked(api.run.files).mockResolvedValue({ items: ["src/main.ts"] });
+    // The prompt is controlled by the page: put the cursor at the end of it.
+    const { spies } = renderSetup({ prompt: "look at @ma" });
+    (box() as HTMLTextAreaElement).setSelectionRange(11, 11);
+    fireEvent.select(box());
+
+    fireEvent.click(await screen.findByText("src/main.ts"));
+    expect(api.run.files).toHaveBeenCalledWith("/Users/tester", "ma");
+    expect(spies.onPromptChange).toHaveBeenLastCalledWith("look at @src/main.ts ");
+  });
+
+  it("offers no slash commands on a codex lane", async () => {
+    renderSetup({ prompt: "", tool: "codex" });
+    fireEvent.change(box(), { target: { value: "/rev" } });
+    await new Promise((r) => setTimeout(r, 20));
+    expect(screen.queryByTestId("prompt-autocomplete")).toBeNull();
+    expect(api.ccConfig.commands).not.toHaveBeenCalled();
+  });
+});