feat(lanes): reorder and rename lane cards, and show each file's line delta

The lane strip's tiles are now drag-reorderable (Alt+←/→ is the keyboard
path), and a lane's name can be set in place from the detail header. The
"Lane 23 ·" prefix is gone from both — the bare `#23` stays on the tile,
because that number is how the CLI addresses a lane.

Card order is a per-viewer preference, not a lane fact: it lives in
localStorage (`agenthub.workspace.laneOrder`) beside the split-view layout
and writes nothing server-side, so `GET /api/lanes` and `agenthub lanes`
keep answering in id order. Renaming is the opposite — it is PATCH
/api/lanes/:id with {title}, the one lane column a user now types into
directly.

That made a patch value reachable by hand for the first time, so
`bindable` now rejects any non-scalar for every PATCHABLE column with
EBADFIELD, and the route answers 400 for that and for the
SQLITE_CONSTRAINT family, rather than handing better-sqlite3 a datatype
throw and reporting 500 on plain bad input.

The uncommitted-files tooltip became a real panel. `GET /api/lanes/:id/git`
now returns `files` as {path, status, added, deleted} records — deltas from
one `git diff --numstat HEAD`, null where git has none to report (untracked,
binary, renamed) — and the card renders them portalled to the body, so the
Workspace's own scroll box cannot clip the list.

client/src/components/lanes/LaneStripCard.tsx

@@ -7,9 +7,15 @@
  * absent: the detail panel's pipeline map below shows the same thing with the
  * stage names attached. Keeping the tile small and fixed-width is what lets
  * many lanes stay scannable in one scrolling row.
+ *
+ * The tile is also the strip's reorder handle: native HTML5 drag-and-drop, no
+ * dependency. Ceiling: desktop pointers only — there is no touch drag and no
+ * auto-scroll when the strip overflows, so Alt+Arrow moves the focused tile as
+ * the keyboard (and touch-free) path.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
+import { useState } from "react";
 import { useTranslation } from "react-i18next";
 import type { Lane } from "../../lib/types";
 
@@ -45,33 +51,69 @@ function detectionLeads(lane: Lane): boolean {
 
 export default function LaneStripCard({
   lane,
+  index,
   selected,
   onSelect,
+  onReorder,
 }: {
   lane: Lane;
+  /** Position in the lane array — the unit both reorder paths speak in. */
+  index: number;
   selected: boolean;
   onSelect: () => void;
+  onReorder: (from: number, to: number) => void;
 }) {
   const { t } = useTranslation(["lanes"]);
+  const [dropTarget, setDropTarget] = useState(false);
 
   return (
     <button
       type="button"
       data-testid={`lane-tile-${lane.id}`}
       data-selected={selected ? "true" : undefined}
+      data-drop-target={dropTarget ? "true" : undefined}
       aria-pressed={selected}
       onClick={onSelect}
-      title={lane.cwd}
-      className={`w-56 shrink-0 rounded-lg border p-3 text-left shadow-sm transition-colors ${
-        selected
-          ? "border-accent bg-accent/10"
-          : "border-border bg-surface-2 hover:border-border-light hover:bg-surface-3"
+      draggable
+      onDragStart={(e) => {
+        // Firefox starts no drag at all without a setData call.
+        e.dataTransfer.setData("text/plain", String(index));
+        e.dataTransfer.effectAllowed = "move";
+      }}
+      onDragOver={(e) => {
+        e.preventDefault();
+        e.dataTransfer.dropEffect = "move";
+        setDropTarget(true);
+      }}
+      onDragLeave={() => setDropTarget(false)}
+      onDragEnd={() => setDropTarget(false)}
+      onDrop={(e) => {
+        e.preventDefault();
+        setDropTarget(false);
+        const from = Number(e.dataTransfer.getData("text/plain"));
+        if (Number.isInteger(from)) onReorder(from, index);
+      }}
+      onKeyDown={(e) => {
+        if (!e.altKey || (e.key !== "ArrowLeft" && e.key !== "ArrowRight")) return;
+        e.preventDefault();
+        onReorder(index, index + (e.key === "ArrowLeft" ? -1 : 1));
+      }}
+      title={`${lane.cwd}\n${t("reorderHint")}`}
+      className={`w-56 shrink-0 cursor-grab rounded-lg border p-3 text-left shadow-sm transition-colors active:cursor-grabbing ${
+        dropTarget
+          ? "border-accent bg-accent/20"
+          : selected
+            ? "border-accent bg-accent/10"
+            : "border-border bg-surface-2 hover:border-border-light hover:bg-surface-3"
       }`}
     >
       <div className="mb-1.5 flex items-center gap-1.5 text-[11px]">
         <span className={`h-2 w-2 shrink-0 rounded-full ${LIVENESS_DOT[lane.liveness]}`} />
-        <span className="shrink-0 text-[10px] font-semibold uppercase tracking-widest text-fg-muted">
-          {t("cardId", { id: lane.id })}
+        {/* The bare id, not "Lane 23": the word cost a third of the row's
+            width and said nothing, but the number itself is how the CLI
+            addresses a lane (`agenthub stage --lane 23`), so it stays. */}
+        <span className="shrink-0 text-[10px] font-semibold tracking-widest text-fg-muted">
+          #{lane.id}
         </span>
         <span className="truncate rounded bg-surface-4 px-1.5 py-0.5 text-fg-secondary">
           {lane.stage}