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__/worktree.test.js

@@ -100,8 +100,16 @@ describe("worktree", () => {
     assert.equal(s.dirty, 1);
     assert.equal(s.untracked, 1); // node_modules is ignored, so it does not count
     assert.match(s.head, /^[0-9a-f]{7,40}$/);
-    // The same lines the counts came from, so a caller can name the files.
-    assert.deepEqual(s.files.sort(), [" M README.md", "?? scratch.txt"]);
+    // The files the counts came from, each with its porcelain status code and
+    // its line delta. An UNTRACKED file has no delta to report — git has never
+    // seen it — so its counts are null rather than invented.
+    assert.deepEqual(
+      s.files.sort((a, b) => a.path.localeCompare(b.path)),
+      [
+        { path: "README.md", status: " M", added: 1, deleted: 0 },
+        { path: "scratch.txt", status: "??", added: null, deleted: null },
+      ]
+    );
     // The fixture has no remotes. Given the lane's base branch, unpushedCount
     // measures base..HEAD — this worktree has committed nothing of its own, so 0.
     assert.equal(await wt.unpushedCount(dir, "main"), 0);