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.

server/__tests__/lanes-api.test.js

@@ -143,6 +143,30 @@ describe("/api/lanes", () => {
     assert.equal((await request("GET", `/api/lanes/${laneId}`)).status, 404);
   });
 
+  // The Workspace's inline rename is a text field PATCHing this route, so a
+  // title is the one lane column a user types directly. Bad input on any
+  // patchable column is a 400: reaching better-sqlite3 with a non-scalar
+  // raises a datatype error Express can only report as a 500.
+  it("renames a lane, and answers 400 rather than 500 for unbindable input", async () => {
+    const created = await request("POST", "/api/lanes", { cwd: "/tmp/lane-rename-route" });
+    const id = created.body.lane.id;
+    const named = await request("PATCH", `/api/lanes/${id}`, { title: "  checkout flow  " });
+    assert.equal(named.status, 200);
+    assert.equal(named.body.lane.title, "checkout flow");
+    const cleared = await request("PATCH", `/api/lanes/${id}`, { title: "" });
+    assert.equal(cleared.body.lane.title, "");
+
+    for (const patch of [{ title: { evil: true } }, { notes: { a: 1 } }, { ci_status: true }]) {
+      const bad = await request("PATCH", `/api/lanes/${id}`, patch);
+      assert.equal(bad.status, 400, `expected 400 for ${JSON.stringify(patch)}`);
+      assert.equal(bad.body.error.code, "EBADFIELD");
+    }
+    // A NOT NULL column patched to null is the caller's mistake too.
+    const notNull = await request("PATCH", `/api/lanes/${id}`, { status: null });
+    assert.equal(notNull.status, 400);
+    assert.equal((await request("DELETE", `/api/lanes/${id}`)).status, 200);
+  });
+
   it("rejects cross-origin lane deletion", async () => {
     const created = await request("POST", "/api/lanes", { cwd: "/tmp/lane-cross-origin-delete" });
     const id = created.body.lane.id;