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/agent/changes.rs

@@ -119,7 +119,6 @@ impl RenderOnce for FileChangeCard {
         let theme = cx.theme();
         let colors = theme.colors.clone();
         div()
-            .w_full()
             .rounded(theme.radius(Radius::Md))
             .border_1()
             .border_color(colors.border)
@@ -270,7 +269,6 @@ impl RenderOnce for MultiFileDiffReview {
                 )
         });
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_2()

src/agent/control.rs

@@ -88,7 +88,6 @@ impl RenderOnce for HumanInputRequest {
         let theme = cx.theme();
         let colors = theme.colors.clone();
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_3()
@@ -177,7 +176,6 @@ impl RenderOnce for CostBreakdown {
             )
         });
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_3()

src/agent/environment.rs

@@ -117,7 +117,6 @@ impl RenderOnce for SandboxStatus {
         let live = matches!(self.state, SandboxState::Starting | SandboxState::Busy);
         let color = self.state.color(&colors);
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_3()

src/agent/memory.rs

@@ -84,7 +84,6 @@ impl RenderOnce for MemoryPanel {
             )
         });
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_3()

src/agent/permission.rs

@@ -137,7 +137,6 @@ impl RenderOnce for PermissionPrompt {
                 })
         };
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_3()

src/agent/progress.rs

@@ -118,7 +118,6 @@ impl RenderOnce for AgentPlan {
             .filter(|(_, state)| *state == StepState::Done)
             .count();
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_2()
@@ -284,7 +283,6 @@ impl RenderOnce for AgentProgress {
         let theme = cx.theme();
         let colors = theme.colors.clone();
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_2()

src/agent/registry.rs

@@ -112,7 +112,6 @@ impl RenderOnce for ToolRegistry {
         let groups = grouped(&self.tools, &found(&self.tools, &self.query));
         let empty = groups.is_empty();
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_4()

src/agent/tools.rs

@@ -109,7 +109,6 @@ impl RenderOnce for ToolCallCard {
                 .child(text)
         };
         div()
-            .w_full()
             .rounded(theme.radius(Radius::Md))
             .border_1()
             .border_color(colors.border)
@@ -217,7 +216,6 @@ impl RenderOnce for ToolCallGroup {
         let theme = cx.theme();
         let colors = theme.colors.clone();
         div()
-            .w_full()
             .flex()
             .flex_col()
             .gap_2()