Improve search autocomplete UX

- Tab key accepts autocomplete suggestion (like right arrow)
- Prevent search from firing while autocomplete suggestion is visible

src/mail/screens/SearchPanel.py

@@ -160,7 +160,6 @@ class SearchPanel(Widget):
         width: auto;
         padding: 0 1;
         color: $primary;
-        height: 1;
     }
 
     SearchPanel Input {
@@ -178,7 +177,6 @@ class SearchPanel(Widget):
         width: auto;
         padding: 0 1;
         color: $text-muted;
-        height: 1;
     }
     """
 
@@ -231,6 +229,34 @@ class SearchPanel(Widget):
             yield Button("?", variant="default", id="help-btn")
             yield Button("Cancel", variant="warning", id="cancel-btn")
 
+    def _has_suggestion(self) -> bool:
+        """Check if the search input currently has an autocomplete suggestion."""
+        try:
+            input_widget = self.query_one("#search-input", Input)
+            return bool(input_widget._suggestion and input_widget._cursor_at_end)
+        except Exception:
+            return False
+
+    def _accept_suggestion(self) -> bool:
+        """Accept the current autocomplete suggestion if present. Returns True if accepted."""
+        try:
+            input_widget = self.query_one("#search-input", Input)
+            if input_widget._suggestion and input_widget._cursor_at_end:
+                input_widget.value = input_widget._suggestion
+                input_widget.cursor_position = len(input_widget.value)
+                return True
+        except Exception:
+            pass
+        return False
+
+    def on_key(self, event) -> None:
+        """Handle key events to intercept Tab for autocomplete."""
+        if event.key == "tab":
+            # Try to accept suggestion; if successful, prevent default tab behavior
+            if self._accept_suggestion():
+                event.prevent_default()
+                event.stop()
+
     def show(self, initial_query: str = "") -> None:
         """Show the search panel and focus the input."""
         self.add_class("visible")
@@ -268,6 +294,10 @@ class SearchPanel(Widget):
 
     def _trigger_search(self) -> None:
         """Trigger the actual search after debounce."""
+        # Don't search if an autocomplete suggestion is visible
+        if self._has_suggestion():
+            return
+
         query = self.query_one("#search-input", Input).value.strip()
         if query and query != self._last_query:
             self._last_query = query