Capture · Roots: roots drop w_full; hosts give the width

145 component roots drop w_full, the early returns included. Three
field rows keep it, Input, InputGroup and TagInput: stretched without
a width, taffy 0.9 laid the field's flex_1 share at no width in the
template picker at 280px, and the placeholder drew nothing. Container
keeps it, since mx_auto needs a width to fill.

Hosts that relied on a root's width now give it: MessageList boxes
each row at the list's width, the splash gives its bar the column's,
and test stages that mount a component as the window's root sit in a
size_full box. Tests hold a narrow row across the list and the splash
bar across its column; each goes red without its fix.

The gallery gains --narrow <px>, which lays each page in a padded
card at that width and shoots it without its script. The page
header wraps: the title takes the room and the theme switcher drops
below, where a long summary used to push it past the edge. A file
panel step waits for the panel to become key instead of a fixed
pause, which lost a race in a capture.

src/calendar/agenda.rs

@@ -142,7 +142,6 @@ impl RenderOnce for AgendaView {
         if owners.is_empty() {
             return div()
                 .debug_selector(|| "agenda-none".into())
-                .w_full()
                 .py_6()
                 .flex()
                 .justify_center()
@@ -172,7 +171,6 @@ impl RenderOnce for AgendaView {
             })
         };
         div()
-            .w_full()
             .child(
                 sections
                     .selected(picked.read(cx).clone())

src/calendar/allday.rs

@@ -119,7 +119,6 @@ impl RenderOnce for AllDayRow {
         });
         div()
             .relative()
-            .w_full()
             .h(pad * 2.0 + pitch * lanes as f32 - gap)
             .border_b_1()
             .border_color(theme.colors.border)

src/calendar/chip.rs

@@ -93,7 +93,6 @@ impl RenderOnce for EventChip {
             .flex()
             .items_center()
             .gap_1()
-            .w_full()
             .h(theme.calendar().chip)
             .px_1p5()
             .rounded(round)

src/calendar/month.rs

@@ -420,7 +420,6 @@ impl RenderOnce for CalendarMonthView {
             .collect();
         let title = shown.strftime("%B %Y").to_string();
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_3()

src/calendar/people.rs

@@ -173,7 +173,6 @@ impl RenderOnce for AttendeeList {
             })
             .collect();
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_1()

src/calendar/year.rs

@@ -300,7 +300,6 @@ impl RenderOnce for YearView {
             })
             .collect();
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_4()