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/lanes/LaneGitHeader.tsx

@@ -13,6 +13,7 @@
 import { useCallback, useEffect, useLayoutEffect, useRef, useState } from "react";
 import { createPortal } from "react-dom";
 import { useTranslation } from "react-i18next";
+import { GitBranch } from "lucide-react";
 import { LaneGitBar } from "./LaneGitBar";
 import { api } from "../../lib/api";
 import { keepIfSame } from "../../lib/keepIfSame";
@@ -230,50 +231,64 @@ export function LaneGitHeader({
   useEffect(() => () => window.clearTimeout(filesCloseTimer.current), []);
 
   if (!git?.available) return null;
-  return (
-    <div data-testid="lane-git-header">
-      {/* One line, because every part of it is short and the panel is
-          narrow: branch, head, subject, and the uncommitted counts read as a
-          sentence rather than a four-row block. */}
-      <div className="mb-2">
-        <div
-          data-testid="lane-git"
-          className="flex items-baseline gap-2 truncate font-mono text-[11px] text-fg-secondary"
-          title={git.subject}
-        >
-          <span className="shrink-0">⑂ {git.branch}</span>
-          <span className="shrink-0 text-fg-muted">{git.head}</span>
-          <span className="truncate text-fg-muted">{git.subject}</span>
-          {(git.dirty > 0 || git.untracked > 0) && (
-            <button
-              type="button"
-              ref={setCountsAnchor}
-              data-testid="lane-git-counts"
-              aria-expanded={filesOpen}
-              onMouseEnter={openFiles}
-              onMouseLeave={closeFiles}
-              // Focus and click open it too: hover is not a gesture a
-              // keyboard or a touchscreen has.
-              onFocus={openFiles}
-              onBlur={closeFiles}
-              onClick={() => setFilesOpen((v) => !v)}
-              className="shrink-0 cursor-help text-status-warning/80 underline decoration-dotted underline-offset-2"
-            >
-              {t("git.uncommitted", { dirty: git.dirty, untracked: git.untracked })}
-            </button>
-          )}
-        </div>
-        {filesOpen && git.files?.length > 0 && (
-          <LaneGitFilesPanel
-            files={git.files}
-            hidden={git.dirty + git.untracked - git.files.length}
-            anchor={countsAnchor}
-            onPointerEnter={openFiles}
-            onPointerLeave={closeFiles}
-          />
-        )}
+  const lead = (
+    <>
+      {/* One row with the actions: branch first and strongest, then the head
+          and its subject, which is what truncates when the panel is narrow
+          (the whole of it stays in the tooltip). */}
+      <div
+        data-testid="lane-git"
+        className="flex min-w-0 flex-1 items-baseline gap-1.5 font-mono text-[11px]"
+        title={`${git.head} ${git.subject}`}
+      >
+        <span className="flex shrink-0 items-center gap-1 self-center font-semibold text-fg-primary">
+          <GitBranch className="h-3 w-3 text-fg-muted" />
+          {git.branch}
+        </span>
+        <span className="shrink-0 text-fg-muted">{git.head}</span>
+        <span className="min-w-0 truncate text-fg-muted">{git.subject}</span>
       </div>
-      <LaneGitBar laneId={laneId} git={git} onChanged={onChanged} onNewLane={onNewLane} />
+      {(git.dirty > 0 || git.untracked > 0) && (
+        <button
+          type="button"
+          ref={setCountsAnchor}
+          data-testid="lane-git-counts"
+          aria-expanded={filesOpen}
+          onMouseEnter={openFiles}
+          onMouseLeave={closeFiles}
+          // Focus and click open it too: hover is not a gesture a
+          // keyboard or a touchscreen has.
+          onFocus={openFiles}
+          onBlur={closeFiles}
+          onClick={() => setFilesOpen((v) => !v)}
+          className="shrink-0 cursor-help rounded-full border border-status-warning/40 bg-status-warning/10 px-2 py-px text-[10.5px] text-status-warning"
+        >
+          {t("git.uncommitted", { dirty: git.dirty, untracked: git.untracked })}
+        </button>
+      )}
+    </>
+  );
+  return (
+    <div
+      data-testid="lane-git-header"
+      className="mb-2 rounded-md border border-border bg-surface-2 px-2 py-1"
+    >
+      <LaneGitBar
+        laneId={laneId}
+        git={git}
+        onChanged={onChanged}
+        onNewLane={onNewLane}
+        lead={lead}
+      />
+      {filesOpen && git.files?.length > 0 && (
+        <LaneGitFilesPanel
+          files={git.files}
+          hidden={git.dirty + git.untracked - git.files.length}
+          anchor={countsAnchor}
+          onPointerEnter={openFiles}
+          onPointerLeave={closeFiles}
+        />
+      )}
     </div>
   );
 }