fix(@angular/ssr): preserve preload metadata for nested empty-path routes

[alan-agius4]

Previously, handleRoute yielded a parent route's metadata before appending loadChildren preloads or traversing child routes, while traverseRoutesConfig appended a trailing slash only to empty-path routes. Under a non-empty parent, the parent ('/pricing') and its empty-path child ('/pricing/') received distinct keys during getRoutesFromAngularRouterConfig deduplication (seenRoutes) and were only merged later by RouteTree.insert. However, when an empty-path route was nested under another empty-path route (such as at the root '/' or under '/es' -> '' -> ''), both the parent and child received the same key, causing seenRoutes to keep the outer route's metadata and drop the descendant's accumulated preload and redirect metadata.

Update handleRoute to append loadChildren preloads upfront and allow the first matching empty-path child route to override its parent's metadata for the same path, and remove the redundant addTrailingSlash keying in traverseRoutesConfig.

Closes #34320

[alan-agius4]

/gemini review

[gemini-code-assist]

Code Review

This pull request updates the Angular SSR routing logic to preserve preload metadata and redirects for nested empty-path routes. It refactors handleRoute to track parent routes using a Map and allows empty-path child routes to override parent metadata, ensuring accumulated preloads are preserved. Additionally, it removes trailing slash additions for empty paths, adds a comprehensive unit test to verify preload preservation, and updates the testing utilities to support entryPointToBrowserMapping in the testing manifest. There are no review comments, so I have no feedback to provide.

[gemini-code-assist]

Code Review

This pull request refactors route traversal in the Angular SSR package to correctly preserve preload metadata and redirects for nested empty-path routes. It introduces a mechanism where empty-path child routes can override parent route metadata, ensuring accumulated preloads are preserved. Additionally, it updates testing utilities to support entryPointToBrowserMapping and adds a test case verifying the preservation of preload metadata. There are no review comments, so I have no feedback to provide.