Make the module navigation capability an optional context member

ModuleUiHostContext.navigation is now `navigation?: ModuleUiNavigation |
undefined`, so the public context change is source-compatible: a context built
before navigation existed (without the member) still compiles unchanged, as
0.x patch releases require. The Dashboard supplies navigation; hosts without
addressable pages, including the display host, omit the member; modules
feature-detect it. Existing hosts' tests are restored to their pre-PR shape,
and a module-ui-sdk test proves a pre-navigation context still satisfies
ModuleUiHostContext (and fails if the member is ever made required).
Runtime behaviour, manifest v8/v9 compatibility, and security rules are
unchanged. ADR 0063 and the module development guide say so.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/module-ui-host/tests/real-artifact.test.ts

@@ -35,7 +35,6 @@ function ekklesiaContext(requested: string[]): ModuleUiHostContext {
     contributions: NO_MODULE_UI_CONTRIBUTIONS,
     display: undefined,
     moduleId: "example",
-    navigation: undefined,
     api: {
       async request(pathname) {
         requested.push(`/api/v1/modules/example/${pathname.replace(/^\//u, "")}`);
@@ -54,7 +53,6 @@ function standaloneContext(requested: string[]): ModuleUiHostContext {
     contributions: NO_MODULE_UI_CONTRIBUTIONS,
     display: { url: "https://example.test/display" },
     moduleId: "example",
-    navigation: undefined,
     api: {
       async request(pathname) {
         requested.push(`https://example.test/api/${pathname.replace(/^\//u, "")}`);