test: assert delegated handlers pop exactly one navigation stack frame

test_handler_delegation! asserted only that the current route equalled the
base block after Esc. When the delegated block was itself the base block the
stack read [base, base], so that assertion held whether or not the sub-handler
popped, and the case asserted nothing.

Capture the navigation stack depth before delegating and assert it drops by
exactly one, which also catches a handler that pops and then re-pushes. Depth
is read through a test-only accessor on App; the navigation_stack field stays
private.

Main tab blocks clear errors on Esc rather than popping, by design, so they
cannot be probed this way at all. Drop them from the delegation value lists;
the remaining values in each list already exercise the same dispatch arm.

src/handlers/radarr_handlers/radarr_handler_tests.rs

@@ -123,7 +123,6 @@ mod tests {
   #[rstest]
   fn test_delegates_system_blocks_to_system_handler(
     #[values(
-      ActiveRadarrBlock::System,
       ActiveRadarrBlock::SystemLogs,
       ActiveRadarrBlock::SystemQueuedEvents,
       ActiveRadarrBlock::SystemTasks,
@@ -142,7 +141,6 @@ mod tests {
   #[rstest]
   fn test_delegates_library_blocks_to_library_handler(
     #[values(
-      ActiveRadarrBlock::Movies,
       ActiveRadarrBlock::MoviesSortPrompt,
       ActiveRadarrBlock::SearchMovie,
       ActiveRadarrBlock::SearchMovieError,
@@ -186,7 +184,6 @@ mod tests {
   #[rstest]
   fn test_delegates_collections_blocks_to_collections_handler(
     #[values(
-      ActiveRadarrBlock::Collections,
       ActiveRadarrBlock::SearchCollection,
       ActiveRadarrBlock::CollectionsSortPrompt,
       ActiveRadarrBlock::SearchCollectionError,
@@ -213,7 +210,6 @@ mod tests {
   fn test_delegates_indexers_blocks_to_indexers_handler(
     #[values(
       ActiveRadarrBlock::DeleteIndexerPrompt,
-      ActiveRadarrBlock::Indexers,
       ActiveRadarrBlock::AllIndexerSettingsPrompt,
       ActiveRadarrBlock::IndexerSettingsAvailabilityDelayInput,
       ActiveRadarrBlock::IndexerSettingsConfirmPrompt,
@@ -237,7 +233,6 @@ mod tests {
   #[rstest]
   fn test_delegates_downloads_blocks_to_downloads_handler(
     #[values(
-      ActiveRadarrBlock::Downloads,
       ActiveRadarrBlock::DeleteDownloadPrompt,
       ActiveRadarrBlock::UpdateDownloadsPrompt
     )]
@@ -253,7 +248,6 @@ mod tests {
   #[rstest]
   fn test_delegates_root_folders_blocks_to_root_folders_handler(
     #[values(
-      ActiveRadarrBlock::RootFolders,
       ActiveRadarrBlock::AddRootFolderPrompt,
       ActiveRadarrBlock::DeleteRootFolderPrompt
     )]
@@ -269,7 +263,6 @@ mod tests {
   #[rstest]
   fn test_delegates_blocklist_blocks_to_blocklist_handler(
     #[values(
-      ActiveRadarrBlock::Blocklist,
       ActiveRadarrBlock::BlocklistItemDetails,
       ActiveRadarrBlock::DeleteBlocklistItemPrompt,
       ActiveRadarrBlock::BlocklistClearAllItemsPrompt,
@@ -287,7 +280,6 @@ mod tests {
   #[rstest]
   fn test_delegates_history_blocks_to_history_handler(
     #[values(
-      ActiveRadarrBlock::History,
       ActiveRadarrBlock::HistoryItemDetails,
       ActiveRadarrBlock::HistorySortPrompt,
       ActiveRadarrBlock::FilterHistory,