Add mini-calendar sidebar to Calendar TUI

- Add MonthCalendar widget as a collapsible sidebar (toggle with 's')
- Sidebar syncs with main week grid (week highlight, selected date)
- Click dates in sidebar to navigate week grid to that date
- Click month navigation arrows to change displayed month
- Add goto_date() method to WeekGrid for date navigation

src/calendar/app.py

@@ -18,6 +18,7 @@ from textual.reactive import reactive
 
 from src.calendar.backend import CalendarBackend, Event
 from src.calendar.widgets.WeekGrid import WeekGrid
+from src.calendar.widgets.MonthCalendar import MonthCalendar
 from src.calendar.widgets.AddEventForm import EventFormData
 from src.utils.shared_config import get_theme_name
 
@@ -52,6 +53,26 @@ class CalendarApp(App):
         layout: vertical;
     }
     
+    #main-content {
+        layout: horizontal;
+        height: 1fr;
+    }
+    
+    #sidebar {
+        width: 26;
+        border-right: solid $surface-darken-1;
+        background: $surface;
+        padding: 1 0;
+    }
+    
+    #sidebar.hidden {
+        display: none;
+    }
+    
+    #sidebar-calendar {
+        height: auto;
+    }
+
     #week-grid {
         height: 1fr;
     }
@@ -98,6 +119,7 @@ class CalendarApp(App):
         Binding("L", "next_week", "Next Week", show=True),
         Binding("g", "goto_today", "Today", show=True),
         Binding("w", "toggle_weekends", "Weekends", show=True),
+        Binding("s", "toggle_sidebar", "Sidebar", show=True),
         Binding("r", "refresh", "Refresh", show=True),
         Binding("enter", "view_event", "View", show=True),
         Binding("a", "add_event", "Add", show=True),
@@ -106,6 +128,7 @@ class CalendarApp(App):
 
     # Reactive attributes
     include_weekends: reactive[bool] = reactive(True)
+    show_sidebar: reactive[bool] = reactive(True)
 
     # Instance attributes
     backend: Optional[CalendarBackend]
@@ -124,7 +147,10 @@ class CalendarApp(App):
     def compose(self) -> ComposeResult:
         """Create the app layout."""
         yield Header()
-        yield WeekGrid(id="week-grid")
+        with Horizontal(id="main-content"):
+            with Vertical(id="sidebar"):
+                yield MonthCalendar(id="sidebar-calendar")
+            yield WeekGrid(id="week-grid")
         yield Static(id="event-detail", classes="hidden")
         yield CalendarStatusBar(id="status-bar")
         yield Footer()
@@ -136,10 +162,23 @@ class CalendarApp(App):
         # Load events for current week
         self.load_events()
 
+        # Sync sidebar calendar with current week
+        self._sync_sidebar_calendar()
+
         # Update status bar and title
         self._update_status()
         self._update_title()
 
+    def _sync_sidebar_calendar(self) -> None:
+        """Sync the sidebar calendar with the main week grid."""
+        try:
+            grid = self.query_one("#week-grid", WeekGrid)
+            calendar = self.query_one("#sidebar-calendar", MonthCalendar)
+            calendar.update_week(grid.week_start)
+            calendar.update_selected(grid.get_cursor_date())
+        except Exception:
+            pass  # Sidebar might not exist yet
+
     def load_events(self) -> None:
         """Load events from backend for the current week."""
         if not self.backend:
@@ -255,11 +294,22 @@ class CalendarApp(App):
     def on_week_grid_week_changed(self, message: WeekGrid.WeekChanged) -> None:
         """Handle week change - reload events."""
         self.load_events()
+        self._sync_sidebar_calendar()
 
     def on_week_grid_event_selected(self, message: WeekGrid.EventSelected) -> None:
         """Handle event selection."""
         self._update_event_detail(message.event)
 
+    # Handle MonthCalendar messages
+    def on_month_calendar_date_selected(
+        self, message: MonthCalendar.DateSelected
+    ) -> None:
+        """Handle date selection from sidebar calendar."""
+        grid = self.query_one("#week-grid", WeekGrid)
+        grid.goto_date(message.date)
+        self.load_events()
+        self._sync_sidebar_calendar()
+
     # Navigation actions (forwarded to grid)
     def action_cursor_down(self) -> None:
         """Move cursor down."""
@@ -311,6 +361,15 @@ class CalendarApp(App):
         mode = "7 days" if self.include_weekends else "5 days (weekdays)"
         self.notify(f"Showing {mode}")
 
+    def action_toggle_sidebar(self) -> None:
+        """Toggle sidebar visibility."""
+        self.show_sidebar = not self.show_sidebar
+        sidebar = self.query_one("#sidebar", Vertical)
+        if self.show_sidebar:
+            sidebar.remove_class("hidden")
+        else:
+            sidebar.add_class("hidden")
+
     def action_refresh(self) -> None:
         """Refresh events from backend."""
         self.load_events()
@@ -383,6 +442,7 @@ Keybindings:
   H/L     - Previous/Next week
   g       - Go to today
   w       - Toggle weekends (5/7 days)
+  s       - Toggle sidebar
   Enter   - View event details
   a       - Add new event
   r       - Refresh

src/calendar/widgets/MonthCalendar.py

@@ -240,3 +240,41 @@ class MonthCalendar(Widget):
         self.display_month = date(year, month, 1)
         self.post_message(self.MonthChanged(self.display_month))
         self.refresh()
+
+    def on_click(self, event) -> None:
+        """Handle mouse clicks on the calendar."""
+        # Row 0 is the month header (< Month Year >)
+        # Row 1 is day names (Mo Tu We ...)
+        # Row 2+ are the week rows
+        y = event.y
+        x = event.x
+
+        if y == 0:
+            # Month header - check for navigation arrows
+            if x < 2:
+                self.prev_month()
+            elif x >= self.size.width - 2:
+                self.next_month()
+            return
+
+        if y == 1:
+            # Day names row - ignore
+            return
+
+        # Week row - calculate which date was clicked
+        week_idx = y - 2
+        weeks = self._weeks
+        if week_idx < 0 or week_idx >= len(weeks):
+            return
+
+        week = weeks[week_idx]
+        # Each day takes 3 characters ("DD "), so find which day column
+        day_col = x // 3
+        if day_col < 0 or day_col >= 7:
+            return
+
+        clicked_date = week[day_col]
+        if clicked_date is not None:
+            self.selected_date = clicked_date
+            self.post_message(self.DateSelected(clicked_date))
+            self.refresh()

src/calendar/widgets/WeekGrid.py

@@ -761,3 +761,20 @@ class WeekGrid(Vertical):
         event = self.get_event_at_cursor()
         if event:
             self.post_message(self.EventSelected(event))
+
+    def goto_date(self, target_date: date) -> None:
+        """Navigate to a specific date.
+
+        Sets the week to contain the target date and places cursor on that day.
+        """
+        # Get the week start for the target date
+        week_start_date = get_week_start_for_date(target_date)
+
+        if self.week_start != week_start_date:
+            self.week_start = week_start_date
+
+        # Set cursor column to the target date
+        col = get_day_column_for_date(target_date, self.week_start)
+        if not self.include_weekends and col >= 5:
+            col = 4  # Last weekday if weekend
+        self.cursor_col = col