Add tools route compatibility redirects

docs/tables_frontend_overhaul_implementation_plan.md

@@ -51,6 +51,7 @@ It is intentionally implementation-focused:
 | 2026-03-21 | Post-P1 fix 3 | Completed | Restored layout-level shell interactivity by rendering routed content in `InteractiveServer` mode, which re-enabled shell event handlers such as the hamburger menu and theme selector. |
 | 2026-03-21 | Post-P1 fix 4 | Completed | Added early theme bootstrapping in `App.razor` and `theme.js` so the stored mode is applied before hydration and remains visible after refresh. |
 | 2026-03-21 | P2.1 | Completed | Added canonical `/tools/diagnostics` and `/tools/api` routes with dedicated tooling page components, extracted the diagnostics and API content into shared tool components, and updated the `Tools` landing page to link to the new route structure. |
+| 2026-03-21 | P2.2 | Completed | Replaced the old `/diagnostics` and `/api` pages with lightweight compatibility routes that reuse a shared redirect component, preserve query strings and fragments, and replace browser history while forwarding into the canonical `Tools` routes. |
 
 ### Lessons Learned
 
@@ -71,6 +72,7 @@ It is intentionally implementation-focused:
 - In Blazor Web Apps, page-level render modes do not automatically make layout-level controls interactive in the way this shell expects. The routed shell itself needs an interactive render boundary.
 - Persisted theme state should be applied before Blazor hydrates, not only after layout initialization. Otherwise refresh can look broken even when storage writes succeed.
 - For route migration in Blazor, extracting the destination UI into shared components keeps canonical routes and temporary compatibility routes from drifting while the redirect phase is still pending.
+- Compatibility routes should stay declarative and shared. A single redirect component is enough for route forwarding and avoids copy-pasted `NavigationManager` lifecycle logic in page files.
 
 ## Target Outcomes
 
@@ -359,7 +361,7 @@ Establish the shared shell, tokens, typography, and theme system that every dest
 | Task | Status | Notes |
 | --- | --- | --- |
 | `P2.1` | Completed | Canonical `Tools` child routes now exist, backed by dedicated route pages and shared tooling content components. |
-| `P2.2` | Pending | Old `/diagnostics` and `/api` routes still need to become compatibility forwards. |
+| `P2.2` | Completed | Old `/diagnostics` and `/api` routes now forward into the canonical `Tools` routes with shared redirect behavior. |
 | `P2.3` | Pending | Recent tables state has not been introduced yet. |
 | `P2.4` | Pending | Pinned tables state has not been introduced yet. |
 | `P2.5` | Pending | Table-context URL parsing and serialization still needs a shared model. |