wire search mode, single-select pills, remove Standard pill

Mode pills are now single-select (tap to activate, tap again to
deactivate) matching the web frontend behavior. Removed the
"Standard" pill — it's the implicit default when no mode is active.

Search mode sends webSearch: true in the ChatRequest body, which
triggers the backend's agentive web search (openrouter:web_search
or Google Search grounding). Sources and query are already parsed
by StreamConsumer and rendered via SourcesBlock/SourceChip.

Active pills now highlighted with accent color + accent border
instead of generic surface alpha, making the active state
visually obvious.

app/src/main/java/dev/kaizen/app/chat/ChatComponents.kt

@@ -142,14 +142,10 @@ fun EmptyHero(userName: String, onPick: (String) -> Unit, modifier: Modifier = M
 }
 
 @Composable
-fun ModePillsRow(selected: Set<Int>, onToggle: (Int) -> Unit, modifier: Modifier = Modifier) {
+fun ModePillsRow(activeMode: Int?, onToggle: (Int) -> Unit, modifier: Modifier = Modifier) {
     val cs = MaterialTheme.colorScheme
     val isDark = isSystemInDarkTheme()
-
-    val glassBorder = remember(isDark) {
-        if (isDark) Brush.verticalGradient(listOf(Color.White.copy(alpha = 0.14f), Color.White.copy(alpha = 0.04f)))
-        else Brush.verticalGradient(listOf(Color.White.copy(alpha = 0.50f), Color.Black.copy(alpha = 0.06f)))
-    }
+    val accent = LocalKaizenAccent.current
 
     Row(
         modifier
@@ -158,25 +154,30 @@ fun ModePillsRow(selected: Set<Int>, onToggle: (Int) -> Unit, modifier: Modifier
             .padding(horizontal = 14.dp),
         horizontalArrangement = Arrangement.spacedBy(8.dp),
     ) {
-        chatModes.forEach { mode ->
+        chatModes.filter { it.labelRes != R.string.mode_standard }.forEach { mode ->
             val label = stringResource(mode.labelRes)
-            val active = mode.labelRes in selected
+            val active = mode.labelRes == activeMode
             val backgroundFill = if (active) {
-                if (isDark) cs.surface.copy(alpha = 0.8f) else cs.surface.copy(alpha = 0.88f)
+                accent.primary.copy(alpha = if (isDark) 0.18f else 0.14f)
             } else {
                 if (isDark) cs.surface.copy(alpha = 0.35f) else cs.surface.copy(alpha = 0.55f)
             }
+            val borderColor = if (active) {
+                accent.primary.copy(alpha = 0.4f)
+            } else {
+                if (isDark) Color.White.copy(alpha = 0.08f) else Color.Black.copy(alpha = 0.06f)
+            }
 
             Row(
                 Modifier
                     .clip(KaizenShapes.pill)
                     .background(backgroundFill)
-                    .border(1.2.dp, glassBorder, KaizenShapes.pill)
+                    .border(1.2.dp, borderColor, KaizenShapes.pill)
                     .clickable { onToggle(mode.labelRes) }
                     .padding(horizontal = 13.dp, vertical = 8.dp),
                 verticalAlignment = Alignment.CenterVertically,
             ) {
-                Icon(mode.icon, null, tint = if (active) cs.onBackground else cs.onSurfaceVariant, modifier = Modifier.size(16.dp))
+                Icon(mode.icon, null, tint = if (active) accent.primary else cs.onSurfaceVariant, modifier = Modifier.size(16.dp))
                 Spacer(Modifier.width(6.dp))
                 Text(label, color = if (active) cs.onBackground else cs.onSurfaceVariant, fontSize = 13.sp, fontWeight = if (active) FontWeight.SemiBold else FontWeight.Medium)
             }

app/src/main/java/dev/kaizen/app/chat/ChatScreen.kt

@@ -97,7 +97,7 @@ fun ChatScreen(
     var input by remember { mutableStateOf("") }
     var isStreaming by remember { mutableStateOf(false) }
     var nextId by remember { mutableStateOf(0L) }
-    var selectedModes by remember { mutableStateOf(setOf(R.string.mode_standard)) }
+    var activeMode by remember { mutableStateOf<Int?>(null) }
 
     // Navigation State
     var currentScreen by remember { mutableStateOf(AppScreen.Chat) }
@@ -339,6 +339,7 @@ fun ChatScreen(
                 KaizenApi.chat(
                     cfg.baseUrl, cfg.token, cfg.model, history, cfg.speed,
                     attachments = uploadedAtts.takeIf { it.isNotEmpty() },
+                    webSearch = activeMode == R.string.mode_search,
                 ).collect { state ->
                     val idx = messages.indexOfLast { it.id == assistantId }
                     if (idx < 0) return@collect
@@ -621,9 +622,9 @@ fun ChatScreen(
                         ) {
                             Spacer(Modifier.height(24.dp))
                             ModePillsRow(
-                                selected = selectedModes,
+                                activeMode = activeMode,
                                 onToggle = { mode ->
-                                    selectedModes = if (mode in selectedModes) selectedModes - mode else selectedModes + mode
+                                    activeMode = if (activeMode == mode) null else mode
                                     haptics.tick()
                                 },
                             )

app/src/main/java/dev/kaizen/app/net/KaizenApi.kt

@@ -35,6 +35,7 @@ import java.util.concurrent.TimeUnit
     val reasoningEffort: String? = null,
     val preferThroughput: Boolean? = null,
     val attachments: List<Attachment>? = null,
+    val webSearch: Boolean? = null,
 )
 
 /** One entry from GET /api/v1/models — the picker's row. `provider == "vertex"` drives the hoster badge. */
@@ -440,6 +441,7 @@ object KaizenApi {
         messages: List<WireMessage>,
         speed: ChatSpeed = ChatSpeed.Normal,
         attachments: List<Attachment>? = null,
+        webSearch: Boolean = false,
     ): Flow<StreamState> = flow {
         val payload = json.encodeToString(
             ChatRequest(
@@ -448,6 +450,7 @@ object KaizenApi {
                 reasoningEffort = speed.reasoningEffort,
                 preferThroughput = if (speed.preferThroughput) true else null,
                 attachments = attachments?.takeIf { it.isNotEmpty() },
+                webSearch = if (webSearch) true else null,
             ),
         ).toRequestBody(jsonMedia)
         val req = Request.Builder()