fix(view,place): the boards view pads clear of the phone's navbar

The panel had an inset for this; the calendar never did. Its root filled the
leaf, and Obsidian's phone navbar floats over a leaf rather than shortening
it, so the scroll container ran to the bottom of the screen and the last row
of the list sat under the bar - unreachable.

`lib/inset.ts` is the same pure measurement the panel plugin grew, with the
same tests: the deeper of navbar and keyboard, never their sum, and a bar that
sits beside the view covers nothing of it. The view re-measures by frame until
it holds still and writes `--bcal-inset-bottom`.

`viewport()` subtracts the bar too, so anchored panels and the quick look are
placed against what is actually reachable instead of ending under it.

tests/place.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import { onScreen, place, roomFor } from "../src/lib/place";
+import { onScreen, place, roomFor, viewport } from "../src/lib/place";
 import type { Box } from "../src/lib/place";
 
 const VIEW = { width: 1280, height: 800 };
@@ -95,3 +95,41 @@ describe("roomFor", () => {
     expect(roomFor({ width: 390, height: 60 })).toBeGreaterThan(100);
   });
 });
+
+// Obsidian's phone navbar is not part of the visual viewport - it floats over
+// it - so a panel sized to the viewport still ends up underneath it.
+describe("viewport minus the floating navbar", () => {
+  function fakeWin(navbarTop: number | null, height = 780): Window {
+    const bar = {
+      getBoundingClientRect: () => ({
+        top: navbarTop ?? 0,
+        bottom: height,
+        height: height - (navbarTop ?? 0),
+        left: 0,
+        right: 390,
+      }),
+      offsetParent: {},
+    };
+    return {
+      innerWidth: 390,
+      innerHeight: height,
+      visualViewport: { width: 390, height, offsetTop: 0, offsetLeft: 0 },
+      document: {
+        querySelector: (selector: string) =>
+          selector === ".mobile-navbar" && navbarTop !== null ? bar : null,
+      },
+    } as unknown as Window;
+  }
+
+  it("takes the navbar off the bottom", () => {
+    expect(viewport(fakeWin(724)).height).toBe(724);
+  });
+
+  it("leaves the height alone with no navbar in the way", () => {
+    expect(viewport(fakeWin(null)).height).toBe(780);
+  });
+
+  it("still leaves a usable strip if a bar somehow covers everything", () => {
+    expect(viewport(fakeWin(0)).height).toBeGreaterThanOrEqual(120);
+  });
+});