fix(plugin-context-navigation): preserve sub-route on context change

The path adapter previously dropped the sub-route on every context
encode, including when context changed (not just when cleared). Only
drop the sub-route when context becomes null, since there's no valid
context to resolve it against.

Fixes: equinor/fusion#904

Author: Noggling

.changeset/plugin-context-navigation_preserve-sub-route-on-context-change.md

@@ -0,0 +1,7 @@
+---
+"@equinor/fusion-framework-plugin-context-navigation": patch
+---
+
+Fix the path adapter to preserve the app's sub-route when the context changes, instead of always resetting to the app root. The sub-route is still dropped when context is cleared entirely, since there's no valid context to resolve it against.
+
+Fixes: https://github.com/equinor/fusion/issues/904

packages/plugins/context-navigation/src/adapters/create-path-adapter.ts

@@ -68,19 +68,21 @@ export function createPathAdapter(): ContextNavigationAdapter {
     /**
      * Encode context into the URL as a path segment.
      *
-     * - **Null context:** removes the context segment to produce a bare app route.
-     * - **Active context:** places/replaces the context id as the segment after the app key.
-     *
-     * Sub-routes after the context segment are intentionally dropped — a context
-     * change resets the app to its root view to avoid landing in an invalid state.
+     * - **Null context:** removes the context segment and drops any sub-route,
+     *   resetting the app to its root view — there's no valid context to resolve
+     *   the sub-route against.
+     * - **Active context:** places/replaces the context id as the segment after
+     *   the app key, preserving the existing sub-route.
      */
     encode({ context, currentURL }: { context: ContextItem | null; currentURL: URL }): URL | null {
       const match = parseAppRoute(currentURL.pathname);
       // Pathname doesn't match the /apps/{key}/... shape — not a Fusion app route, bail out
       if (!match) return null;
 
       const targetPath =
-        context === null ? buildAppRoute(match.appKey) : buildAppRoute(match.appKey, context.id);
+        context === null
+          ? buildAppRoute(match.appKey)
+          : buildAppRoute(match.appKey, context.id, match.rest);
 
       const url = new URL(targetPath, currentURL.origin);
       url.search = currentURL.search;