Add search functionality to Mail TUI with / keybinding

- Add reusable SearchScreen modal and ClearableSearchInput widget
- Implement filter_by_query in MessageStore for client-side filtering
- Search matches subject, sender name/email, recipient name/email
- Press / to open search, Escape to clear search filter
- Shows search query in list subtitle when filter is active

src/mail/app.py

@@ -11,6 +11,7 @@ from src.services.taskwarrior import client as taskwarrior_client
 from src.services.himalaya import client as himalaya_client
 from src.utils.shared_config import get_theme_name
 from src.utils.ipc import IPCListener, IPCMessage
+from src.utils.search import SearchScreen
 from textual.containers import Container, ScrollableContainer, Vertical, Horizontal
 from textual.timer import Timer
 from textual.binding import Binding
@@ -73,6 +74,7 @@ class EmailViewerApp(App):
     sort_order_ascending: Reactive[bool] = reactive(True)
     selected_messages: Reactive[set[int]] = reactive(set())
     main_content_visible: Reactive[bool] = reactive(True)
+    search_query: Reactive[str] = reactive("")  # Current search filter
 
     def get_system_commands(self, screen: Screen) -> Iterable[SystemCommand]:
         yield from super().get_system_commands(screen)
@@ -126,6 +128,7 @@ class EmailViewerApp(App):
             Binding("x", "toggle_selection", "Toggle selection", show=False),
             Binding("space", "toggle_selection", "Toggle selection"),
             Binding("escape", "clear_selection", "Clear selection"),
+            Binding("/", "search", "Search"),
         ]
     )
 
@@ -511,7 +514,13 @@ class EmailViewerApp(App):
 
         config = get_config()
 
-        for item in self.message_store.envelopes:
+        # Use filtered envelopes if search is active
+        if self.search_query:
+            display_envelopes = self.message_store.filter_by_query(self.search_query)
+        else:
+            display_envelopes = self.message_store.envelopes
+
+        for item in display_envelopes:
             if item and item.get("type") == "header":
                 # Use the new GroupHeader widget for date groupings
                 envelopes_list.append(ListItem(GroupHeader(label=item["label"])))
@@ -872,10 +881,17 @@ class EmailViewerApp(App):
             self._update_list_view_subtitle()
 
     def action_clear_selection(self) -> None:
-        """Clear all selected messages."""
-        self.selected_messages.clear()
-        self.refresh_list_view_items()  # Refresh all items to uncheck checkboxes
-        self._update_list_view_subtitle()
+        """Clear all selected messages and search filter."""
+        if self.selected_messages:
+            self.selected_messages.clear()
+            self.refresh_list_view_items()  # Refresh all items to uncheck checkboxes
+            self._update_list_view_subtitle()
+        elif self.search_query:
+            # Clear search if no selection
+            self.search_query = ""
+            self._populate_list_view()
+            self._update_list_view_subtitle()
+            self.show_status("Search cleared")
 
     def action_oldest(self) -> None:
         self.fetch_envelopes() if self.reload_needed else None
@@ -885,6 +901,40 @@ class EmailViewerApp(App):
         self.fetch_envelopes() if self.reload_needed else None
         self.show_message(self.message_store.get_newest_id())
 
+    def action_search(self) -> None:
+        """Open search dialog to filter messages."""
+
+        def handle_search_result(query: str | None) -> None:
+            if query is None:
+                return  # User cancelled
+            self.search_query = query
+            self._apply_search_filter()
+
+        self.push_screen(
+            SearchScreen(
+                title="Search Messages",
+                placeholder="Search by subject, sender, or recipient...",
+                initial_value=self.search_query,
+            ),
+            handle_search_result,
+        )
+
+    def _apply_search_filter(self) -> None:
+        """Apply the current search filter to the envelope list."""
+        self._populate_list_view()
+
+        # Update the title to show search status
+        if self.search_query:
+            self.query_one("#envelopes_list").border_subtitle = f"[{self.search_query}]"
+        else:
+            self._update_list_view_subtitle()
+
+        # Focus the list and select first message
+        self.query_one("#envelopes_list").focus()
+        envelopes_list = self.query_one("#envelopes_list", ListView)
+        if envelopes_list.children:
+            envelopes_list.index = 0
+
     def action_focus_1(self) -> None:
         self.query_one("#envelopes_list").focus()