Investigate navigation-compose @Composable surface; no-op changes reverted

[Copilot]

Xamarin.AndroidX.Navigation.Compose ships several *Kt wrappers (NavHostKt, NavGraphBuilderKt, DialogHostKt, NavHostControllerKt, NavBackStackEntryProviderKt), and part of the @Composable navigation surface (NavHost, NavGraphBuilder.composable, NavGraphBuilder.navigation, NavBackStackEntry.LocalOwnersProvider) is unreachable from C#.

Outcome

This PR ended up making no net change — the originally proposed edits were inert and have been reverted. The branch now has no diff versus base.

Why the original changes did nothing

• PublicAPI/PublicAPI.Unshipped.txt is a generated file. Directory.Build.targets (_GeneratePublicApiFiles, AfterTargets="Build") regenerates it from the compiled assembly on every build, so hand-written method entries never affect what is bound — they are overwritten to match the generator's actual output. The methods originally listed (DialogHost, dialog, rememberNavController, currentBackStackEntryAsState) are already bound today; the baseline was merely stale.
• config.json 2.9.8 → 2.9.8.1 only changes the package version. With no Metadata/Transforms change, the produced API is identical, so it would have shipped an empty version bump.

Root cause of the empty surface (unchanged, still out of scope)

The generator silently drops any Java method whose parameter/return types can't be resolved to a managed type (warning BG8605). The remaining empty members (NavHost, NavGraphBuilder.composable, NavGraphBuilder.navigation, NavBackStackEntry.LocalOwnersProvider) reference types that are intentionally unbound repo-wide:

• androidx.compose.animation.* — AnimatedContentScope, AnimatedContentTransitionScope, EnterTransition, ExitTransition, SizeTransform. The animation, animation-android, animation-core-android, and animation-graphics bindings each strip their package with <remove-node path="/api/package" />, so they produce zero C# types.
• androidx.compose.runtime.saveable.SaveableStateHolder, androidx.compose.runtime.snapshots.SnapshotStateList.

These cannot bind until androidx.compose.animation (and compose.runtime.saveable) are themselves bound. That is a large, separate cross-library effort: the packages are deliberately stripped via remove-node, and an add-node shim is not viable because the generated C# would reference types that don't exist. Tracked as the real blocker behind this Compose surface, to be handled as its own work item.

[jonathanpeppers]

@copilot this PR does nothing?!?

[Copilot]

@copilot this PR does nothing?!?

You're right — it did nothing, and I've reverted both changes (24b8... is the latest commit; the branch now has no net diff).

Why the original changes were inert:

1. PublicAPI.Unshipped.txt is a generated file. Directory.Build.targets (_GeneratePublicApiFiles, AfterTargets="Build") regenerates it from the compiled assembly on every build, so my hand-written method entries were never going to survive — they don't add any binding, they just get overwritten to match whatever the generator actually emitted.
2. The config.json 2.9.8 → 2.9.8.1 bump only changes the package version; with no Metadata/Transforms change the produced API is byte-for-byte identical, so it would have shipped an empty version bump.

The methods I claimed to "newly bind" (DialogHost, dialog, rememberNavController, currentBackStackEntryAsState) are already bound today — the baseline was just stale.

The genuinely empty surface (NavHost, NavGraphBuilder.composable/navigation, LocalOwnersProvider) is dropped because its signatures reference androidx.compose.animation.*, which is fully stripped repo-wide (<remove-node path="/api/package"/> in animation, animation-android, animation-core-android, animation-graphics) plus compose.runtime.saveable/snapshots. There is no surgical fix here — it requires actually binding the animation packages first, which is a separate, much larger effort. Happy to scope that as its own work item if you'd like.