fix(chat): make context meter strictly backend-reported

Remove misleading local/cumulative token fallback in ContextDetailSheet and hide 0% badge when context used is unknown.

app/src/main/java/com/m57/hermescontrol/ui/chat/components/ContextDetailSheet.kt

@@ -51,12 +51,12 @@ fun ContextDetailSheet(
         sheetState = sheetState,
     ) {
         val full = fullTokens ?: 0L
-        val used = usedTokens ?: breakdown.inputTokens
-        val fraction = if (full > 0L) min(1f, used.toFloat() / full.toFloat()) else 0f
+        val fraction = if (full > 0L && usedTokens != null) min(1f, usedTokens.toFloat() / full.toFloat()) else 0f
         val pct = (fraction * 100).toInt()
         val statusColors = LocalHermesStatusColors.current
         val barColor =
             when {
+                usedTokens == null -> MaterialTheme.colorScheme.primary
                 pct >= 90 -> statusColors.error
                 pct >= 70 -> statusColors.warning
                 else -> MaterialTheme.colorScheme.primary
@@ -83,7 +83,7 @@ fun ContextDetailSheet(
                 verticalAlignment = Alignment.Bottom,
             ) {
                 Text(
-                    text = formatTokens(used),
+                    text = if (usedTokens != null) formatTokens(usedTokens) else "—",
                     style = MaterialTheme.typography.headlineSmall,
                     fontWeight = FontWeight.Bold,
                     color = barColor,
@@ -115,7 +115,12 @@ fun ContextDetailSheet(
                 )
             }
             Text(
-                text = "$pct% of context window used",
+                text =
+                    if (usedTokens != null) {
+                        "$pct% of context window used"
+                    } else {
+                        stringResource(R.string.context_window_usage_unavailable)
+                    },
                 style = MaterialTheme.typography.labelMedium,
                 color = MaterialTheme.colorScheme.onSurfaceVariant,
             )

app/src/main/java/com/m57/hermescontrol/ui/chat/components/ContextUsageChip.kt

@@ -56,12 +56,12 @@ fun ContextUsageChip(
     val full = fullTokens
     if (full == null || full <= 0L) return
 
-    val used = usedTokens ?: 0L
-    val fraction = min(1f, used.toFloat() / full.toFloat())
+    val fraction = if (usedTokens != null) min(1f, usedTokens.toFloat() / full.toFloat()) else 0f
     val pct = (fraction * 100).toInt()
     val statusColors = LocalHermesStatusColors.current
     val barColor =
         when {
+            usedTokens == null -> MaterialTheme.colorScheme.primary
             pct >= 90 -> statusColors.error
             pct >= 70 -> statusColors.warning
             else -> MaterialTheme.colorScheme.primary
@@ -90,7 +90,7 @@ fun ContextUsageChip(
             Text(
                 text =
                     if (usedTokens != null) {
-                        "${formatTokens(used)} / ${formatTokens(full)} context"
+                        "${formatTokens(usedTokens)} / ${formatTokens(full)} context"
                     } else {
                         "— / ${formatTokens(full)} context"
                     },
@@ -111,12 +111,14 @@ fun ContextUsageChip(
                         maxLines = 1,
                     )
                 }
-                Text(
-                    text = "$pct%",
-                    style = MaterialTheme.typography.labelSmall,
-                    color = barColor,
-                    maxLines = 1,
-                )
+                if (usedTokens != null) {
+                    Text(
+                        text = "$pct%",
+                        style = MaterialTheme.typography.labelSmall,
+                        color = barColor,
+                        maxLines = 1,
+                    )
+                }
             }
         }
         Box(