feat: add Trends sidebar nav item + 3-view switching (Task E.2)

IMPLEMENTATION_PLAN.md

@@ -265,16 +265,16 @@ Comprehensive review and improvement of all Plotly charts in the Dash dashboard.
 - **Checkpoint**: Patient Pathways has 9 tabs (Icicle through Doses, no Trends). `python run_dash.py` starts cleanly. PASSED.
 
 ### E.2 Add Trends sidebar nav item + view container
-- [ ] Add `"trends"` icon SVG to `_ICONS` dict in `dash_app/components/sidebar.py` — use a line chart icon: `<polyline points="22 12 18 12 15 21 9 3 6 12 2 12"/>`
+- [x] Add `"trends"` icon SVG to `_ICONS` dict in `dash_app/components/sidebar.py` — use a line chart icon: `<polyline points="22 12 18 12 15 21 9 3 6 12 2 12"/>`
-- [ ] Add `_sidebar_item("Trends", "trends", active=False, item_id="nav-trends")` to sidebar children
+- [x] Add `_sidebar_item("Trends", "trends", active=False, item_id="nav-trends")` to sidebar children
-- [ ] Add `html.Div(id="trends-view", style={"display": "none"}, children=[...])` to `app.py` layout inside `view-container`, after `trust-comparison-view`
+- [x] Add `html.Div(id="trends-view", style={"display": "none"}, children=[...])` to `app.py` layout inside `view-container`, after `trust-comparison-view`
-- [ ] Update `switch_view()` in `dash_app/callbacks/navigation.py`:
+- [x] Update `switch_view()` in `dash_app/callbacks/navigation.py`:
   - Add `Output("trends-view", "style")` and `Output("nav-trends", "className")` — now 3 views, 3 nav items (6 outputs total)
   - Handle 3-way switching: `"patient-pathways"`, `"trust-comparison"`, `"trends"`
-- [ ] Update `update_app_state()` in `dash_app/callbacks/filters.py`:
+- [x] Update `update_app_state()` in `dash_app/callbacks/filters.py`:
   - Add `Input("nav-trends", "n_clicks")`
   - Add `elif triggered_id == "nav-trends": active_view = "trends"` case
-- **Checkpoint**: 3 sidebar items visible. Clicking "Trends" switches to empty trends view. `python run_dash.py` starts cleanly.
+- **Checkpoint**: 3 sidebar items visible. Clicking "Trends" switches to empty trends view. `python run_dash.py` starts cleanly. PASSED.
 
 ### E.3 Create Trends landing page — directorate-level trends
 - [ ] Create `dash_app/components/trends.py`:
@@ -354,8 +354,8 @@ Comprehensive review and improvement of all Plotly charts in the Dash dashboard.
 - [x] `python run_dash.py` starts cleanly
 
 ### Phase E
-- [ ] Trends tab removed from Patient Pathways (9 tabs remain)
+- [x] Trends tab removed from Patient Pathways (9 tabs remain)
-- [ ] 3rd sidebar item "Trends" visible and functional
+- [x] 3rd sidebar item "Trends" visible and functional
 - [ ] Trends landing page shows directorate-level line chart with metric toggle
 - [ ] Clicking a directorate drills into drug-level trends
 - [ ] Back button returns to directorate overview

dash_app/app.py

@@ -29,6 +29,7 @@ app.layout = dmc.MantineProvider(
             "selected_trusts": [],
             "active_view": "patient-pathways",
             "selected_comparison_directorate": None,
+            "selected_trends_directorate": None,
         }),
         dcc.Store(id="chart-data", storage_type="memory"),
         dcc.Store(id="reference-data", storage_type="session"),
@@ -64,6 +65,14 @@ app.layout = dmc.MantineProvider(
                                 make_tc_dashboard(),
                             ],
                         ),
+                        # Trends view (hidden initially)
+                        html.Div(
+                            id="trends-view",
+                            style={"display": "none"},
+                            children=[
+                                html.H3("Trends", style={"padding": "24px"}),
+                            ],
+                        ),
                     ],
                 ),
                 make_footer(),

dash_app/callbacks/filters.py

@@ -75,13 +75,14 @@ def register_filter_callbacks(app):
         Input("trust-chips", "value"),
         Input("nav-patient-pathways", "n_clicks"),
         Input("nav-trust-comparison", "n_clicks"),
+        Input("nav-trends", "n_clicks"),
         Input({"type": "tc-selector", "index": ALL}, "n_clicks"),
         Input("tc-back-btn", "n_clicks"),
         State("app-state", "data"),
     )
     def update_app_state(
         _dir_clicks, _ind_clicks, initiated, last_seen, selected_drugs,
-        selected_trusts, _nav_pp_clicks, _nav_tc_clicks,
+        selected_trusts, _nav_pp_clicks, _nav_tc_clicks, _nav_trends_clicks,
         _tc_selector_clicks, _tc_back_clicks, current_state
     ):
         """Update app-state when any filter, nav, or TC selector changes."""
@@ -96,6 +97,7 @@ def register_filter_callbacks(app):
                 "selected_trusts": [],
                 "active_view": "patient-pathways",
                 "selected_comparison_directorate": None,
+                "selected_trends_directorate": None,
             }
 
         triggered_id = ctx.triggered_id
@@ -114,6 +116,8 @@ def register_filter_callbacks(app):
             active_view = "patient-pathways"
         elif triggered_id == "nav-trust-comparison":
             active_view = "trust-comparison"
+        elif triggered_id == "nav-trends":
+            active_view = "trends"
 
         # Trust Comparison directorate selection
         selected_comparison_directorate = current_state.get("selected_comparison_directorate")

dash_app/callbacks/navigation.py

@@ -1,4 +1,4 @@
-"""Callbacks for view switching between Patient Pathways and Trust Comparison."""
+"""Callbacks for view switching between Patient Pathways, Trust Comparison, and Trends."""
 from dash import Input, Output
 
 
@@ -8,22 +8,27 @@ def register_navigation_callbacks(app):
     @app.callback(
         Output("patient-pathways-view", "style"),
         Output("trust-comparison-view", "style"),
+        Output("trends-view", "style"),
         Output("nav-patient-pathways", "className"),
         Output("nav-trust-comparison", "className"),
+        Output("nav-trends", "className"),
         Input("app-state", "data"),
     )
     def switch_view(app_state):
         """Show/hide views and update sidebar active state based on active_view."""
-        if not app_state:
-            return {}, {"display": "none"}, "sidebar__item sidebar__item--active", "sidebar__item"
-
-        view = app_state.get("active_view", "patient-pathways")
         show = {}
         hide = {"display": "none"}
         active_cls = "sidebar__item sidebar__item--active"
         inactive_cls = "sidebar__item"
 
+        if not app_state:
+            return show, hide, hide, active_cls, inactive_cls, inactive_cls
+
+        view = app_state.get("active_view", "patient-pathways")
+
         if view == "patient-pathways":
-            return show, hide, active_cls, inactive_cls
+            return show, hide, hide, active_cls, inactive_cls, inactive_cls
-        else:
+        elif view == "trust-comparison":
-            return hide, show, inactive_cls, active_cls
+            return hide, show, hide, inactive_cls, active_cls, inactive_cls
+        else:  # trends
+            return hide, hide, show, inactive_cls, inactive_cls, active_cls

dash_app/components/sidebar.py

@@ -20,6 +20,7 @@ def _svg_icon(svg_body):
 _ICONS = {
     "pathway": '<rect x="3" y="3" width="7" height="7"/><rect x="14" y="3" width="7" height="7"/><rect x="14" y="14" width="7" height="7"/><rect x="3" y="14" width="7" height="7"/>',
     "compare": '<line x1="18" y1="20" x2="18" y2="10"/><line x1="12" y1="20" x2="12" y2="4"/><line x1="6" y1="20" x2="6" y2="14"/>',
+    "trends": '<polyline points="22 12 18 12 15 21 9 3 6 12 2 12"/>',
 }
 
 
@@ -41,6 +42,10 @@ def make_sidebar():
                         "Trust Comparison", "compare",
                         active=False, item_id="nav-trust-comparison",
                     ),
+                    _sidebar_item(
+                        "Trends", "trends",
+                        active=False, item_id="nav-trends",
+                    ),
                 ],
             ),
             html.Div(