Fix command palette over focused scratchpad

The stdin loop's scratchpad-input branch ran before the palette branch
and silently dropped every byte except a handful of app-level chords,
so palette typing and Esc never reached the palette while a pad was
focused. Skip the pad-input branch whenever st.palette != nil.

closePalette also called repaintFocused() on cancel / no-op action
paths, which paints the empty focused-child slot (focusedID == "" while
a pad is focused) and leaves the palette's top border drawn over the
pad. Route those branches through a restoreView helper that picks
repaintFocusedPad when a pad is focused.

Switching from a pad to a child via the palette now clears the pad
focus and wipes the viewport, matching focusProcess's pad-exit path.

Adds a harness scenario (palette_over_scratchpad) that opens a pad,
opens the palette, types a query, and verifies that Esc leaves the
pad correctly repainted with no palette chrome lingering.

internal/app/app.go

@@ -1178,7 +1178,11 @@ func (st *uiState) processStdin(chunk []byte) {
 		// palette, Ctrl-WASD focus, Ctrl-B scrollback) fall through to
 		// the handlers below; everything else is swallowed silently so
 		// typing into a pad view can't leak to a child PTY.
-		if st.focusedPad != "" {
+		//
+		// When the palette is open we skip this block entirely so the
+		// palette handler below receives every byte. Otherwise typing
+		// (and Esc) get swallowed here and the palette appears wedged.
+		if st.focusedPad != "" && st.palette == nil {
 			if b == 0x1b { // ESC or CSI
 				if n := csiLen(chunk, i); n > 0 {
 					final := chunk[i+n-1]
@@ -1553,16 +1557,32 @@ func (st *uiState) closePalette(action paletteAction) {
 	st.outMu.Unlock()
 	st.clearScreen()
 
+	// When a scratchpad is focused, the "main viewport" is showing the
+	// pad's rendered body, not a child PTY. repaintFocused() would draw
+	// an empty state (focusedID == "") and leave the previous palette's
+	// top border visible in the pad area. Use the pad-aware helper for
+	// any branch below that wants to restore the prior view.
+	restoreView := func() {
+		st.mu.Lock()
+		padFocused := st.focusedPad != ""
+		st.mu.Unlock()
+		if padFocused {
+			st.repaintFocusedPad()
+			return
+		}
+		st.repaintFocused()
+	}
+
 	switch action.kind {
 	case "", "cancel":
-		st.repaintFocused()
+		restoreView()
 		st.drawTabBar()
 		st.drawSidebar()
 		st.drawStatusLine()
 
 	case "spawn-agent":
 		if action.preset == nil {
-			st.repaintFocused()
+			restoreView()
 			return
 		}
 		l := st.layoutSnapshot()
@@ -1575,7 +1595,7 @@ func (st *uiState) closePalette(action paletteAction) {
 
 	case "spawn-process":
 		if action.preset == nil {
-			st.repaintFocused()
+			restoreView()
 			return
 		}
 		l := st.layoutSnapshot()
@@ -1586,7 +1606,7 @@ func (st *uiState) closePalette(action paletteAction) {
 
 	case "spawn-process-submit":
 		if action.command == "" {
-			st.repaintFocused()
+			restoreView()
 			return
 		}
 		l := st.layoutSnapshot()
@@ -1617,16 +1637,24 @@ func (st *uiState) closePalette(action paletteAction) {
 	case "switch":
 		c := st.sess.FindChild(action.childID)
 		if c == nil || (c.Kind == KindAgent && c.Status() != StatusRunning) {
-			st.repaintFocused()
+			restoreView()
 			return
 		}
 		layout := st.layoutSnapshot()
 		st.mu.Lock()
+		leavingPad := st.focusedPad != ""
+		st.focusedPad = ""
 		st.focusedID = action.childID
 		st.focusedName = c.DisplayName()
 		st.updateActiveAgentLocked(c)
 		st.renderer = newViewportRenderer(layout)
 		st.mu.Unlock()
+		// Switching from a pad to a child: wipe the pad body so the
+		// child's snapshot paints onto a clean canvas, mirroring
+		// focusProcess.
+		if leavingPad {
+			st.clearViewportArea()
+		}
 		st.repaintFocused()
 		st.drawTabBar()
 		st.drawSidebar()