fix(frontend): make fullscreen chat panel scrollable

frontend/src/pages/LaunchView.vue

@@ -2436,6 +2436,7 @@ watch(
   overflow: hidden;
   display: flex;
   flex-direction: column;
+  min-height: 0;
 }
 
 .chat-messages::-webkit-scrollbar {

openspec/changes/fix-fullscreen-chat-scroll/proposal.md

@@ -0,0 +1,12 @@
+# Change: Fix Fullscreen Chat Panel Scrolling
+
+## Why
+After the persistent chat panel refactoring (commits `5525813` and `d796015`), the fullscreen chat mode is no longer scrollable. When the chat panel is in fullscreen mode (`viewMode === 'chat'`), messages accumulate but users cannot scroll through them.
+
+## What Changes
+- Fix CSS flexbox chain in `LaunchView.vue` so that `overflow-y: auto` on `.chat-messages` activates correctly in fullscreen mode
+- Add `min-height: 0` to intermediate flex containers (`.chat-panel-content` and `.chat-box`) to allow them to shrink below their content size
+
+## Impact
+- Affected specs: chat-panel (new capability spec)
+- Affected code: `frontend/src/pages/LaunchView.vue` (CSS only, ~2–3 lines)

openspec/changes/fix-fullscreen-chat-scroll/specs/chat-panel/spec.md

@@ -0,0 +1,14 @@
+## ADDED Requirements
+
+### Requirement: Fullscreen Chat Scrolling
+The chat messages area SHALL be scrollable when the chat panel is in fullscreen mode and messages exceed the visible viewport height.
+
+#### Scenario: Messages overflow in fullscreen chat
+- **WHEN** the chat panel is in fullscreen mode (`viewMode === 'chat'`)
+- **AND** the number of chat messages exceeds the visible area
+- **THEN** the `.chat-messages` container SHALL allow vertical scrolling via `overflow-y: auto`
+
+#### Scenario: Scroll position preserved on new message
+- **WHEN** the user is scrolled to the bottom of the chat
+- **AND** a new message arrives
+- **THEN** the chat SHALL auto-scroll to show the latest message

openspec/changes/fix-fullscreen-chat-scroll/tasks.md

@@ -0,0 +1,7 @@
+## 1. Implementation
+- [x] 1.1 Add `min-height: 0` to `.chat-panel-content` in `LaunchView.vue`
+- [x] 1.2 Add `min-height: 0` to `.chat-box` in `LaunchView.vue`
+
+## 2. Verification
+- [x] 2.1 Run `openspec validate fix-fullscreen-chat-scroll --strict --no-interactive`
+- [ ] 2.2 Manual visual test: open app, verify fullscreen chat scrolls when messages overflow