feat: v2.5.5 — AI Router renamed AI Proxy, reload onto new builds, update no longer spins

AI Proxy (was AI Router):
- server/lib/ai-proxies.js, proxy-apply.js, routes/ai-proxies.js mounted at
  /api/ai-proxies and the old /api/ai-routers; `router` still accepted on the
  start routes; profiles move to <CLAUDE_HOME>/agenthub-proxies/
- dashboard_runs.router renamed in place to proxy: an older build on the same
  DB fails on that column, so dev and prod sharing one DB update together
- a proxy's baseUrl stored as its root (a typed /v1 made /v1/v1/messages);
  Test probes Claude /v1/messages and Codex /v1/responses
- Settings → AI Proxy (/settings/ai-router redirects), ProxyPicker

Updates:
- every tab reloads onto the new UI build when its WebSocket reconnects to a
  server of another version (lib/newBuildReload.ts, once per version)
- Update now stops waiting on a plugin chain that failed or pulled nothing
  (the old server never goes down), and reloads as soon as a new version answers

Also:
- a pane whose command exits at once says so (EPANEEXITED) instead of
  "Command failed: tmux set-option … mouse on"
- the pane drag preview draws where the pane actually lands

client/src/components/run/__tests__/PaneGrid.test.ts

@@ -0,0 +1,36 @@
+/**
+ * @file PaneGrid.test.ts
+ * @description The pane drop preview: it draws where the dragged pane will
+ * actually land (`dropPreview` over `applyDrop`), not half of the target's
+ * current box, and nothing for a drop that changes nothing.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { describe, expect, it } from "vitest";
+import { dropPreview } from "../PaneGrid";
+import { pane, split, type PaneLayout } from "../../../lib/paneLayout";
+
+const AB: PaneLayout = { root: split("row", pane(0), pane(1)), focus: 0 };
+
+describe("dropPreview", () => {
+  it("a shown pane leaves its place first: A onto B's top is the whole top half", () => {
+    expect(dropPreview(AB, 0, 1, "top")).toEqual({ slot: 0, x: 0, y: 0, w: 1, h: 0.5 });
+  });
+
+  it("a pane from another tab splits the target's current box", () => {
+    expect(dropPreview(AB, 2, 1, "bottom")).toEqual({ slot: 2, x: 0.5, y: 0.5, w: 0.5, h: 0.5 });
+  });
+
+  it("the center swaps into the target's box", () => {
+    expect(dropPreview(AB, 0, 1, "center")).toEqual({ slot: 0, x: 0.5, y: 0, w: 0.5, h: 1 });
+  });
+
+  it("nothing on its own pane or on a refused move", () => {
+    expect(dropPreview(AB, 0, 0, "left")).toBeNull();
+    const full: PaneLayout = {
+      root: split("row", split("col", pane(0), pane(1)), split("col", pane(2), pane(3))),
+      focus: 0,
+    };
+    expect(dropPreview(full, 5, 0, "left")).toBeNull();
+  });
+});