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/LaneChangesPanel.tsx

@@ -630,12 +630,12 @@ export function LaneChangesPanel({
   return (
     <div data-testid="lane-changes" className="flex min-h-0 flex-1 flex-col">
       <LaneGitHeader laneId={laneId} git={git} onChanged={rereadAll} onNewLane={onNewLane} />
-      {/* Two rows on purpose: WHERE you are (mode, and the refresh that always
-          applies) on top, HOW you are looking at it (range, layout, context,
-          whole file) underneath. One row wrapped mid-group as soon as the
-          panel was narrow, which is every panel beside a console. */}
-      <div className="mb-2 space-y-1.5">
-        <div className="flex items-center gap-1.5">
+      {/* ONE wrapping row: where you are (mode) then how you are looking at it
+          (range, layout, context, whole file), refresh last. Each group is
+          its own inline box, so a narrow panel wraps BETWEEN groups — never
+          through one, which is what made the old single row unreadable. */}
+      <div className="mb-2 flex flex-wrap items-center gap-1.5">
+        <div className="contents">
           {mode === "file" ? (
             <button
               type="button"
@@ -677,14 +677,14 @@ export function LaneChangesPanel({
             onClick={rereadAll}
             aria-label={t("changes.refresh")}
             title={t("changes.refresh")}
-            className="ml-auto shrink-0 text-fg-muted hover:text-fg-primary"
+            className="order-last ml-auto shrink-0 text-fg-muted hover:text-fg-primary"
           >
             <RefreshCw className={`h-3.5 w-3.5 ${loading ? "animate-spin" : ""}`} />
           </button>
         </div>
 
         {mode !== "history" && mode !== "browse" && (
-          <div className="flex flex-wrap items-center gap-1.5">
+          <div className="contents">
             <div className="flex items-center rounded border border-border bg-surface-2 p-0.5">
               {(["work", "branch"] as const).map((r) => (
                 <button