Add mouse support to the TUI (tmux-style tile resize)

Enable mouse in the Bubble Tea program. In the layout grid editor:
click a cell to assign a camera, or press on a tile and drag to
resize its span (grid-snapped). Click-to-select on the menu/list
screens and the camera picker. Works over SSH; edits the config,
so it never fights the daemon geometry.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/tui/mouse.go

@@ -0,0 +1,132 @@
+package tui
+
+import tea "github.com/charmbracelet/bubbletea"
+
+// Layout offsets for hit-testing the rendered views (see view.go). Every
+// screen renders a title line then a blank line before its content, so content
+// starts at headerRows. The grid is drawn with a border between cells, hence
+// the +1s.
+const (
+	headerRows = 2          // title line + blank line
+	cellStride = cellW + 1  // cell inner width + right border column
+	blockH     = cellH + 1  // cell content rows + top border row
+)
+
+// handleMouse routes mouse events per screen. Enables click-to-select on the
+// list screens and tmux-style click/drag editing in the layout grid.
+func (m *model) handleMouse(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
+	switch m.screen {
+	case screenMenu, screenCameras, screenLayouts, screenSetActive:
+		return m.mouseList(msg)
+	case screenLayoutEdit:
+		return m.mouseGridEdit(msg)
+	case screenCameraPicker:
+		return m.mousePicker(msg)
+	}
+	return m, nil
+}
+
+// cellAtMouse maps a screen position to a grid cell in the editor/picker.
+func (m *model) cellAtMouse(x, y int) (col, row int, ok bool) {
+	cols, rows := m.gridDims()
+	if y < headerRows || x < 0 {
+		return 0, 0, false
+	}
+	row = (y - headerRows) / blockH
+	col = x / cellStride
+	if row < 0 || row >= rows || col < 0 || col >= cols {
+		return 0, 0, false
+	}
+	return col, row, true
+}
+
+// gridLineCount is how many terminal rows renderGrid emits.
+func (m *model) gridLineCount() int {
+	_, rows := m.gridDims()
+	return rows*blockH + 1
+}
+
+// listLen is the number of selectable rows on the current list screen.
+func (m *model) listLen() int {
+	switch m.screen {
+	case screenMenu:
+		return len(menuItems)
+	case screenCameras:
+		return len(m.cfg.Cameras)
+	case screenLayouts, screenSetActive:
+		return len(m.cfg.Layouts)
+	}
+	return 0
+}
+
+// mouseList: left-click a row to select and activate it (same as pressing enter).
+func (m *model) mouseList(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
+	if msg.Action != tea.MouseActionRelease || msg.Button != tea.MouseButtonLeft {
+		return m, nil
+	}
+	idx := msg.Y - headerRows
+	if idx < 0 || idx >= m.listLen() {
+		return m, nil
+	}
+	m.cursor = idx
+	return m.handleKey(tea.KeyMsg{Type: tea.KeyEnter})
+}
+
+// mouseGridEdit implements tmux-style editing: click a cell to assign a camera,
+// or press on a tile and drag to resize its span (grid-snapped).
+func (m *model) mouseGridEdit(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
+	if msg.Button != tea.MouseButtonLeft {
+		return m, nil
+	}
+	col, row, ok := m.cellAtMouse(msg.X, msg.Y)
+	switch msg.Action {
+	case tea.MouseActionPress:
+		if !ok {
+			return m, nil
+		}
+		m.edCol, m.edRow = col, row
+		m.dragTile = m.tileIndexAt(col, row)
+		m.dragging = m.dragTile >= 0
+		m.dragMoved = false
+
+	case tea.MouseActionMotion:
+		if !ok || !m.dragging {
+			return m, nil
+		}
+		t := &m.curLayout().Tiles[m.dragTile]
+		newCS, newRS := col-t.Col+1, row-t.Row+1
+		// Only grow/shrink toward the bottom-right of the tile's origin.
+		if newCS >= 1 && newRS >= 1 && m.regionFree(m.dragTile, t.Col, t.Row, newCS, newRS) {
+			t.ColSpan, t.RowSpan = newCS, newRS
+			m.edCol, m.edRow = col, row
+			m.dragMoved = true
+			m.dirty = true
+		}
+
+	case tea.MouseActionRelease:
+		wasDrag := m.dragging && m.dragMoved
+		m.dragging = false
+		m.dragMoved = false
+		// A plain click (no drag) opens the camera picker for that cell.
+		if ok && !wasDrag {
+			m.edCol, m.edRow = col, row
+			m.screen, m.cursor = screenCameraPicker, 0
+		}
+	}
+	return m, nil
+}
+
+// mousePicker: left-click an option to choose it.
+func (m *model) mousePicker(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
+	if msg.Action != tea.MouseActionRelease || msg.Button != tea.MouseButtonLeft {
+		return m, nil
+	}
+	// Options are drawn below the grid and a blank separator line.
+	optStart := headerRows + m.gridLineCount() + 1
+	idx := msg.Y - optStart
+	if idx < 0 || idx >= len(m.pickerOptions()) {
+		return m, nil
+	}
+	m.cursor = idx
+	return m.handleKey(tea.KeyMsg{Type: tea.KeyEnter})
+}