feat(share): export the share-view codec and link-path helpers (#1419)

* feat(share): export the share-view codec for host servers

Add `@gods-eye-view/core/share/view-codec` (src/share/viewCodec.js) as a
package export with its own boundary group. The codec is pure (no DOM, no
Cesium, no external dependencies), so a host's server can decode a
/share/<code> link, for example to describe the view in link previews.

* feat(share): export the share-link address helpers

Add `@gods-eye-view/core/share/link-path` (src/share/shareLinkPath.js), so a
host's server reads /share/<code> addresses the way the app does.

package.json

@@ -223,6 +223,8 @@
     "./data/lifecycle": "./src/data/lifecycle.js",
     "./ui/navigation": "./src/ui/navigationController.js",
     "./ui/share-restoration": "./src/ui/shareRestoration.js",
+    "./share/view-codec": "./src/share/viewCodec.js",
+    "./share/link-path": "./src/share/shareLinkPath.js",
     "./ui/visual-settings": "./src/ui/visualSettings.js",
     "./ui/panel-chrome": "./src/ui/panelChrome.js",
     "./layers/flights/records": "./src/layers/flights/records.js",