fix(ui): stabilize footer spinner sizing and user bubble wrapping

Context: UI redesign introduced oversized preferred width on streaming indicator and removed effective width constraint for user message bubbles.

Change: Set spinner preferred width to 0 (kept max stretch behavior) and constrain user message text layout via JTextArea columns; removed ineffective maximumSize constraint in BorderLayout bubble.

Risk: Low. UI layout behavior only; protocol/runtime logic untouched.

Tests: ./gradlew.bat test --tests 'dev.curt.codexjb.ui.ChatPanelTest' --tests 'dev.curt.codexjb.ui.ChatPanelDebounceTest' (JDK 21)

Verification: BUILD SUCCESSFUL (exit code 0).

Swarm: awaiter agent used for targeted test execution.

Author: Codex Agent

src/main/kotlin/dev/curt/codexjb/ui/ChatPanel.kt

@@ -279,7 +279,7 @@ class ChatPanel(
         footer.layout = BoxLayout(footer, BoxLayout.Y_AXIS)
 
         // Row 1: Thin full-width streaming indicator
-        spinner.preferredSize = Dimension(Int.MAX_VALUE, 2)
+        spinner.preferredSize = Dimension(0, 2)
         spinner.maximumSize = Dimension(Int.MAX_VALUE, 2)
         spinner.alignmentX = Component.LEFT_ALIGNMENT
         footer.add(spinner)
@@ -744,11 +744,11 @@ class ChatPanel(
         val area = JTextArea(text)
         area.lineWrap = true
         area.wrapStyleWord = true
+        area.columns = 50
         area.isEditable = false
         area.isOpaque = false
         area.foreground = ChatPalette.bubbleForeground
         area.border = null
-        area.maximumSize = Dimension(450, Int.MAX_VALUE)
         bubble.add(area, BorderLayout.CENTER)
 
         // Right-align user messages