Replace sidebar with responsive app shell

docs/tables_frontend_overhaul_implementation_plan.md

@@ -42,6 +42,7 @@ It is intentionally implementation-focused:
 | 2026-03-21 | P1.2 | Completed | Switched the app to Fraunces, IBM Plex Sans, and IBM Plex Mono with distinct display, body, UI, and code font roles instead of one shared heading font. |
 | 2026-03-21 | P1.3 | Completed | Added explicit light, dark, and system theme modes in the token layer and introduced a scoped `ThemeState` service for later shell controls. |
 | 2026-03-21 | P1.4 | Completed | Added shared browser-storage wrappers, persisted theme mode in `localStorage`, and initialize/apply theme state from the layout on interactive render. |
+| 2026-03-21 | P1.5 | Completed | Replaced the permanent sidebar layout with a sticky top app shell and mobile bottom navigation backed by dedicated shell components. |
 
 ### Lessons Learned
 
@@ -53,6 +54,7 @@ It is intentionally implementation-focused:
 - The old typography setup coupled display and utility text under a single token. The new shell work needs separate display and UI font roles to avoid decorative type in controls.
 - Theme mode selection can be prepared independently of persistence. Splitting those concerns keeps the theme CSS and the storage wiring reviewable.
 - Shared UI state events in Blazor should stay synchronous unless the event contract is async-aware. Layout refresh can be triggered safely with `InvokeAsync(StateHasChanged)` from a synchronous handler.
+- Extracting shell markup into dedicated components is lower-risk than continuing to evolve `MainLayout.razor` directly. It isolates responsive frame work from page content and keeps later nav changes localized.
 
 ## Target Outcomes
 
@@ -258,7 +260,7 @@ Create the implementation foundation so the visual overhaul does not start with
 | `P1.2` | Completed | Font loading now uses Fraunces, IBM Plex Sans, and IBM Plex Mono with explicit role-based tokens. |
 | `P1.3` | Completed | Explicit light, dark, and system modes now exist in CSS, backed by a scoped `ThemeState` service. |
 | `P1.4` | Completed | Theme mode now persists through a shared storage service and is applied from the layout during interactive startup. |
-| `P1.5` | Pending | Shell replacement follows once tokens and theme plumbing exist. |
+| `P1.5` | Completed | The sidebar is gone; pages now render inside a sticky top-shell with a mobile bottom nav. |
 | `P1.6` | Pending | Shell slots and nav utilities depend on the new shell. |
 | `P1.7` | Pending | Skip link and landmark work will land with the shell markup. |
 | `P1.8` | Pending | Tools-specific shell emphasis is final Phase 1 polish. |