fix(mobile): let the map show one day again

Collapsing a day card has hidden that day's places from the map since #216, and
it was the only way to reduce a busy map to one day. The phone shell does not
render DayPlanSidebar, so when it replaced the desktop page on phones that
control disappeared with it: expandedDayIds stayed null and every day's pins sat
on top of each other with nothing to do about it (#1962).

A day chip in map view now drives the same declutter the desktop chevron drives,
rather than introducing a second filter. Entering the map focuses the selected
day, tapping another chip moves the focus with it, and leaving the map clears it
so the timeline is never looking at a filtered state. Unplanned places stay
visible, exactly as the collapse path has always left them.

client/src/mobile/screens/trip/MTripShell.tsx

@@ -225,6 +225,15 @@ export default function MTripShell({
     if (trTab !== 'plan') planner.handleTabChange('plan')
   }
 
+  // Map focus on the selected day. Drives the same declutter the desktop sidebar's
+  // collapse chevron drives (#216) rather than adding a second filter — the phone
+  // lost that affordance when this shell replaced DayPlanSidebar, so a day's pins
+  // could not be told apart from the rest of the trip at all (#1962). Unplanned
+  // places stay visible either way, which is what the collapse path has always done.
+  const focusMapOnDay = (dayId: number | null) => {
+    planner.setExpandedDayIds(dayId == null ? null : new Set([dayId]))
+  }
+
   const toggleView = () => {
     const next = view === 'plan' ? 'map' : 'plan'
     setView(next)
@@ -234,6 +243,11 @@ export default function MTripShell({
     if (next === 'map') {
       planner.setRouteShown(true)
       if (planner.selectedDayId != null) planner.handleSelectDay(planner.selectedDayId, false)
+      focusMapOnDay(planner.selectedDayId)
+    } else {
+      // Leaving the map: nothing is filtered while the timeline is up, so the next
+      // visit starts from the whole trip unless a day is picked again.
+      focusMapOnDay(null)
     }
   }
 
@@ -267,8 +281,12 @@ export default function MTripShell({
     if (dayId === planner.selectedDayId) openSheet('day', { dayId })
     else {
       planner.handleSelectDay(dayId, view !== 'map')
-      // In map mode a day tap fits to that day's places AND draws its route.
-      if (view === 'map') planner.setRouteShown(true)
+      // In map mode a day tap fits to that day's places, draws its route and drops
+      // the other days' pins, so the day it framed is the day it shows.
+      if (view === 'map') {
+        planner.setRouteShown(true)
+        focusMapOnDay(dayId)
+      }
     }
   }
 

client/tests/unit/mobile/trip/MTripShell.test.tsx

@@ -257,6 +257,36 @@ describe('MTripShell', () => {
     expect(planner.setRouteShown).toHaveBeenCalledWith(true)
   })
 
+  // #1962 — the phone lost the desktop sidebar's collapse chevron, so the map showed
+  // every day's pins at once with no way to narrow it down.
+  it('FE-MOB-SHELL-040: entering the map focuses it on the selected day', () => {
+    const { planner } = renderShell()
+    fireEvent.click(screen.getByRole('button', { name: 'mobileTrip.mapView' }))
+    expect(planner.setExpandedDayIds).toHaveBeenCalledWith(new Set([11]))
+  })
+
+  it('FE-MOB-SHELL-041: a day tap in map mode moves the focus with it', () => {
+    const { planner } = renderShell()
+    fireEvent.click(screen.getByRole('button', { name: 'mobileTrip.mapView' }))
+    vi.mocked(planner.setExpandedDayIds).mockClear()
+    fireEvent.click(screen.getByRole('button', { name: 'Sun 3' }))
+    expect(planner.setExpandedDayIds).toHaveBeenCalledWith(new Set([12]))
+  })
+
+  it('FE-MOB-SHELL-042: a day tap in list mode leaves the map unfiltered', () => {
+    const { planner } = renderShell()
+    fireEvent.click(screen.getByRole('button', { name: 'Sun 3' }))
+    expect(planner.setExpandedDayIds).not.toHaveBeenCalled()
+  })
+
+  it('FE-MOB-SHELL-043: leaving the map clears the focus again', () => {
+    const { planner } = renderShell()
+    fireEvent.click(screen.getByRole('button', { name: 'mobileTrip.mapView' }))
+    vi.mocked(planner.setExpandedDayIds).mockClear()
+    fireEvent.click(screen.getByRole('button', { name: 'mobileTrip.listView' }))
+    expect(planner.setExpandedDayIds).toHaveBeenCalledWith(null)
+  })
+
   it('FE-MOB-SHELL-023: the dock only shows enabled tabs and marks the active one', () => {
     const { planner } = renderShell({
       TRIP_TABS: [