drag-pane

# Drag-to-Resize Pane Implementation ## Overview Add drag-to-resize support for two-pane plugin layouts (sidebar + main content). Users click and drag the divider between panes to resize them. ## Prerequisites - Plugin already has a two-pane layout (sidebar + main content) - State persistence functions exist in `internal/state/state.go` (each plugin has its own getter/setter) - Familiarity with `internal/mouse` package ## Existing Implementations | Plugin | State Functions | Mouse File | |--------|----------------|------------| | FileBrowser | `GetFileBrowserTreeWidth()` / `SetFileBrowserTreeWidth()` | `internal/plugins/filebrowser/mouse.go` | | GitStatus | `GetGitStatusSidebarWidth()` / `SetGitStatusSidebarWidth()` | `internal/plugins/gitstatus/mouse.go` | | Conversations | `GetConversationsSideWidth()` / `SetConversationsSideWidth()` | `internal/plugins/conversations/mouse.go` | | Workspace (project) | `GetWorkspaceSidebarWidth()` / `SetWorkspaceSidebarWidth()` | `internal/plugins/workspace/view_list.go` | | Sessions (global workspace) | `GetWorkspaceSidebarWidth()` / `SetWorkspaceSidebarWidth()` | `internal/overview/workspaces.go` | ## Windowing parity: project and global workspaces are one feature The project workspace (`internal/plugins/workspace`) and the global Workspaces browser shown as **Sessions** in the navbar (`internal/overview`) are two projections of the same windowing model. They are not independent surfaces that happen to look similar. **If a change...