Fix explorer back and session usage selection

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

@@ -30,7 +30,7 @@ import java.time.OffsetDateTime
  * own, so the only thing its Back could ever have meant was "put this away".
  */
 @Composable
-fun UsageDialog(feed: UsageFeed, onDismiss: () -> Unit) {
+fun UsageDialog(feed: UsageFeed, session: SessionSummary, onDismiss: () -> Unit) {
     // A plain Dialog rather than an AlertDialog, for the spacing alone. AlertDialog fixes the gaps
     // between its title, content and buttons at sizes meant for a sentence of prose and a decision;
     // this is a dense read-out, and those gaps left a band of empty dialog above Close that was
@@ -45,10 +45,6 @@ fun UsageDialog(feed: UsageFeed, onDismiss: () -> Unit) {
                     verticalAlignment = Alignment.CenterVertically,
                     modifier = Modifier.fillMaxWidth(),
                 ) {
-                    // Deliberately not subtitled with the provider this was opened from. These
-                    // numbers belong to an account on a particular machine -- naming the session's
-                    // provider here made an echo session's screen read "echo" above a line reading
-                    // "claude". Each machine names itself and the service it came from.
                     Text(
                         "Usage",
                         style = MaterialTheme.typography.headlineSmall,
@@ -65,10 +61,24 @@ fun UsageDialog(feed: UsageFeed, onDismiss: () -> Unit) {
                 }
                 Spacer(Modifier.height(8.dp))
                 // Scrolls rather than being trimmed: a machine can report any number of windows and
-                // there can be any number of machines, and a dialog is the one place where running
-                // out of room is silent. `fill = false` so a short read-out keeps a short dialog.
+                // a provider can report several billing pools, and a dialog is the one place where
+                // running out of room is silent. `fill = false` so a short read-out keeps a short
+                // dialog.
                 Column(Modifier.weight(1f, fill = false).verticalScroll(rememberScrollState())) {
-                    UsageBody(feed.snapshots)
+                    val state =
+                        when (val snapshots = feed.snapshots) {
+                            is LoadState.Loading -> LoadState.Loading
+                            is LoadState.Error -> snapshots
+                            is LoadState.Loaded ->
+                                LoadState.Loaded(
+                                    usageSnapshotsFor(
+                                        snapshots.value,
+                                        session.setup,
+                                        session.usageProvider,
+                                    )
+                                )
+                        }
+                    UsageBody(state)
                 }
                 TextButton(onClick = onDismiss, modifier = Modifier.align(Alignment.End)) {
                     Text("Close")
@@ -87,18 +97,18 @@ private fun UsageBody(state: LoadState<List<UsageSnapshot>>) {
             is LoadState.Error -> Text(current.message, color = MaterialTheme.colorScheme.error)
             is LoadState.Loaded ->
                 if (current.value.isEmpty()) {
-                    // Not an error and not a blank screen: no machine offers a paid service, so
+                    // Not an error and not a blank screen: this provider has no paid quota, so
                     // there is genuinely nothing to report and saying so is the answer.
                     Text(
-                        "No machine here runs anything with usage limits.",
+                        "This session's provider has no usage limits.",
                         style = MaterialTheme.typography.bodyMedium,
                         color = MaterialTheme.colorScheme.onSurfaceVariant,
                     )
                 } else {
-                    // No card around each machine. A card is a step up the surface ladder, and
-                    // inside a dialog -- itself a raised surface -- the step barely renders while
-                    // costing 16dp on every side. What separates one machine from the next is the
-                    // line naming it.
+                    // No card around each pool. A card is a step up the surface ladder, and inside
+                    // a dialog -- itself a raised surface -- the step barely renders while costing
+                    // 16dp on every side. What separates one pool from the next is the line naming
+                    // it.
                     current.value.forEachIndexed { index, snapshot ->
                         if (index > 0) {
                             Spacer(Modifier.height(20.dp))