Draw verbatim text on its own dark surface

A command, a tool's output and a code block in a reply are the one thing on
this screen that is not somebody's prose, and they now say so: Mocha's
Crust, which sits below Base, so the same colour is one clear step down both
on the page where a reply is drawn and on the card where a tool call is.

The renderer's code background was `surfaceVariant`, which is exactly a
card's own fill -- a fenced block inside a tool call had no background at
all, and one in a reply read as a step *up* out of the page.

Tool output takes the monospace face with it. It is column-aligned far more
often than it is prose -- a listing, a diff, a table of numbers -- and a
proportional font silently destroys the alignment that carried the meaning.

`RawBlock` is a composable rather than a modifier because the inset is part
of it: monospace text against the edge of a tinted block reads as clipping.
A call with neither a subject nor any other field draws nothing at all
rather than an empty tinted rectangle.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/androidApp/src/main/kotlin/com/example/aiapp/ToolRows.kt

@@ -32,6 +32,7 @@ import androidx.compose.ui.layout.onGloballyPositioned
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.text.font.FontFamily
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
@@ -375,7 +376,17 @@ fun ToolCard(
                 if (tool.output.isNotEmpty()) {
                     Spacer(Modifier.height(8.dp))
                     Text("Output", style = MaterialTheme.typography.labelSmall)
-                    Text(tool.output, style = MaterialTheme.typography.bodySmall)
+                    // What the tool printed, on the surface everything verbatim gets and in the
+                    // face it was written for: this is column-aligned far more often than it is
+                    // prose -- a directory listing, a diff, a table of numbers -- and a
+                    // proportional font silently destroys the alignment that carried the meaning.
+                    RawBlock(Modifier.padding(top = 2.dp)) {
+                        Text(
+                            tool.output,
+                            style = MaterialTheme.typography.bodySmall,
+                            fontFamily = FontFamily.Monospace,
+                        )
+                    }
                 }
             }
             // Shown open or closed. A call that produced a picture is one