fix: keep empty-session launch controls visually attached

The active empty-session composer used the same launch controls as the new-session surface but rendered them outside the glass panel, creating an inconsistent gap between the prompt box and project/branch/worktree selectors. Embed the desktop hero launch row in the composer panel and keep the existing mobile and post-message context-chip paths unchanged.

Constraint: Preserve the existing new-session composer layout and shared RepositoryLaunchControls behavior.
Rejected: Adjust outer margins only | would keep the active empty-session DOM structurally different from the already-correct new-session composer.
Confidence: high
Scope-risk: narrow
Tested: cd desktop && bun run test -- src/components/chat/ChatInput.test.tsx src/pages/EmptySession.test.tsx
Tested: cd desktop && bun run lint
Tested: git diff --check
Tested: agent-browser DOM check confirmed the launch row is inside chat-input-panel with 1px bottom gap
Not-tested: Full bun run verify gate

desktop/src/components/chat/ChatInput.test.tsx

@@ -320,9 +320,16 @@ describe('ChatInput file mentions', () => {
 
     render(<ChatInput variant="hero" />)
 
+    const panel = screen.getByTestId('chat-input-panel')
+    expect(panel).toHaveClass('rounded-xl')
+    expect(panel).not.toHaveClass('rounded-b-none')
+
     expect(await screen.findByRole('button', { name: /Select branch: main/ })).toBeInTheDocument()
     expect(screen.getByText('Current worktree')).toBeInTheDocument()
     expect(screen.queryByText('Select a project...')).not.toBeInTheDocument()
+    const branchButton = screen.getByRole('button', { name: /Select branch: main/ })
+    expect(panel).toContainElement(branchButton.parentElement)
+    expect(branchButton.parentElement).toHaveClass('bg-transparent')
   })
 
   it('uses the persisted message count to keep reopened sessions in context mode while history loads', async () => {

desktop/src/components/chat/ChatInput.tsx

@@ -151,6 +151,7 @@ export function ChatInput({ variant = 'default', compact = false }: ChatInputPro
   const useCompactControls = compact || isMobileComposer
   const iconOnlyAction = compact || isMobileComposer
   const activeLaunchWorkDir = showLaunchControls ? (launchWorkDir || resolvedWorkDir || '') : (resolvedWorkDir || '')
+  const embedLaunchControlsInHero = isHeroComposer && !useCompactControls && showLaunchControls
   const pendingSlashUiAction = !isMemberSession && input.trim().startsWith('/')
     ? resolveSlashUiAction(input.trim().slice(1))
     : null
@@ -802,7 +803,7 @@ export function ChatInput({ variant = 'default', compact = false }: ChatInputPro
         <div
           data-testid="chat-input-panel"
           className={isHeroComposer
-            ? 'glass-panel relative flex flex-col gap-3 rounded-t-xl rounded-b-none p-4 transition-colors'
+            ? `glass-panel relative flex flex-col gap-3 ${embedLaunchControlsInHero ? 'rounded-xl' : 'rounded-t-xl rounded-b-none'} p-4 transition-colors`
             : compact
               ? `glass-panel relative p-3 transition-colors ${isMobileComposer ? 'rounded-2xl shadow-[0_-12px_36px_rgba(54,35,28,0.12)]' : 'rounded-xl'}`
               : `glass-panel relative transition-colors ${isMobileComposer ? 'rounded-2xl p-3 shadow-[0_-12px_36px_rgba(54,35,28,0.12)]' : 'rounded-xl p-4'}`}
@@ -1049,11 +1050,27 @@ export function ChatInput({ variant = 'default', compact = false }: ChatInputPro
               </button>
             </div>
           </div>
+
+          {embedLaunchControlsInHero && (
+            <div className="-mx-4 -mb-4 mt-3">
+              <RepositoryLaunchControls
+                workDir={activeLaunchWorkDir}
+                onWorkDirChange={handleLaunchWorkDirChange}
+                branch={launchBranch}
+                onBranchChange={setLaunchBranch}
+                useWorktree={launchUseWorktree}
+                onUseWorktreeChange={setLaunchUseWorktree}
+                onLaunchReadyChange={setLaunchReady}
+                disabled={isActive || launchTransitioning}
+                placement="composer"
+              />
+            </div>
+          )}
         </div>
 
         <input ref={fileInputRef} type="file" multiple className="hidden" onChange={handleFileSelect} />
 
-        {!isMemberSession && (
+        {!isMemberSession && !embedLaunchControlsInHero && (
           <div className={useCompactControls ? 'mt-2 flex min-w-0 px-1' : 'mt-3 px-1'}>
             {messageCount > 0 ? (
               <ProjectContextChip