feat: add a tool that links to an area in the app

Add open_in_gods_eye_view. It builds a version 2 share link looking
straight down on an area, with altitude chosen from the area's size, on
the app address the application supplies.

src/tools/queries/share.js

@@ -0,0 +1,55 @@
+/** A link that opens God's Eye View on an area. */
+
+import { defineTool, ToolError } from '../catalog.js';
+import { AREA_SCHEMA, areaCenter, areaRadiusKm, resolveArea } from '../area.js';
+
+const MIN_ALTITUDE_M = 500;
+const MAX_ALTITUDE_M = 15_000_000;
+// A top-down view sees roughly this many meters of ground per meter of altitude.
+const GROUND_PER_ALTITUDE = 0.55;
+
+export const openInGodsEyeView = defineTool({
+  name: 'open_in_gods_eye_view',
+  title: "Open in God's Eye View",
+  description:
+    "A link that opens God's Eye View looking straight down on an area.",
+  inputSchema: {
+    type: 'object',
+    properties: { area: AREA_SCHEMA },
+    required: ['area'],
+    additionalProperties: false,
+  },
+  requires: ['app'],
+  async run(args, { services, signal }) {
+    let base;
+    try {
+      base = new URL(services.app.baseUrl);
+    } catch {
+      throw new ToolError('unavailable', "The app's address is not configured");
+    }
+    const area = await resolveArea(args.area, { services, signal });
+    const center = areaCenter(area);
+    const altitude = Math.round(
+      Math.min(
+        MAX_ALTITUDE_M,
+        Math.max(
+          MIN_ALTITUDE_M,
+          (areaRadiusKm(area) * 1000) / GROUND_PER_ALTITUDE,
+        ),
+      ),
+    );
+    // The share-link camera fields; the app restores its defaults for the rest.
+    base.hash = new URLSearchParams({
+      v: '2',
+      lat: center.lat.toFixed(4),
+      lon: center.lon.toFixed(4),
+      alt: String(altitude),
+      heading: '0',
+      pitch: '-90',
+    }).toString();
+    return {
+      summary: `Open ${area.label} in God's Eye View: ${base.href}`,
+      data: { url: base.href, center, altitude_m: altitude },
+    };
+  },
+});