refactor: convert to bun-workspaces monorepo (desktop/ + www/)

- Move the Tauri app (React frontend + Rust backend) into desktop/ via
  git mv — configs unchanged (relative paths: tauri.conf.json, vite.config.ts)
- Root package.json becomes a private bun workspace container with
  orchestration scripts; desktop package renamed gridline-desktop
- Scaffold www/ with Astro 7 + Tailwind v4 (hand-wired vite plugin,
  static output, ready for Dokploy)
- Update release.yml for the new layout: projectPath: desktop,
  desktop/src-tauri resource paths, rust-cache workspace path
- Update README + AGENTS.md structure trees and dev commands
- Verified: vitest (1074), cargo test (354), desktop build, tauri dev
  (window launches), tauri build (dmg + app bundles), Astro build

desktop/src/lib/recentConnections.test.ts

@@ -0,0 +1,18 @@
+import { describe, it, expect } from "vitest";
+import { pruneRecent, dedupeRecent } from "./recentConnections";
+import type { RecentConnection } from "./types";
+
+const rc = (id: string, at: string): RecentConnection => ({ connection_id: id, opened_at: at });
+
+describe("recentConnections helpers", () => {
+  it("pruneRecent keeps the newest N", () => {
+    const list = [rc("a", "1"), rc("b", "3"), rc("c", "2")];
+    expect(pruneRecent(list, 2)).toEqual([rc("b", "3"), rc("c", "2")]);
+  });
+  it("dedupeRecent moves the latest occurrence of an id to the front", () => {
+    const list = [rc("a", "1"), rc("b", "2"), rc("a", "3")];
+    const out = dedupeRecent(list);
+    expect(out[0].connection_id).toBe("a");
+    expect(out).toHaveLength(2);
+  });
+});