feat: add persistent server-client sessions

   Make herdr persistent by default.

   Launching herdr now starts or reattaches to a background session
   server. Clients can detach and reattach while panes and agent
   processes keep running. Session mode now supports multi-client attach,
   auto-detect startup, and a thin-client/headless-server split.

   This also refactors the large app, ui, input, pane, config,
   workspace, and persistence modules into smaller focused submodules,
   while preserving behavior and colocating tests with the code they
   exercise.

   Upgrade notes:
   - persistence mode is now the default
   - in-app quit detaches the current client instead of stopping the server
   - use `herdr server stop` to stop the background session
   - use `--no-session` for the old single-process behavior
   - default socket paths now live under the config directory

1 files changed, 210 insertions, 0 deletions

diff --git a/src/ui/menus.rs b/src/ui/menus.rs
new file mode 100644
index 00000000..537ac9a1
--- /dev/null
+++ b/src/ui/menus.rs
@@ -0,0 +1,210 @@
+use ratatui::{
+    layout::{Alignment, Rect},
+    style::{Modifier, Style},
+    text::{Line, Span},
+    widgets::{Clear, List, ListItem, ListState, Paragraph},
+    Frame,
+};
+
+use super::widgets::{panel_contrast_fg, render_panel_shell};
+use crate::app::AppState;
+
+fn render_bottom_bar(frame: &mut Frame, area: Rect, line: Line<'_>, bg: ratatui::style::Color) {
+    frame.render_widget(Clear, area);
+    let buf = frame.buffer_mut();
+    for x in area.x..area.x + area.width {
+        buf[(x, area.y)].set_style(Style::default().bg(bg));
+    }
+    frame.render_widget(Paragraph::new(line), area);
+}
+
+pub(super) fn render_navigate_overlay(app: &AppState, frame: &mut Frame, area: Rect) {
+    let key = Style::default()
+        .fg(app.palette.accent)
+        .add_modifier(Modifier::BOLD);
+    let dim = Style::default().fg(app.palette.overlay0);
+
+    let mode_style = Style::default()
+        .fg(panel_contrast_fg(&app.palette))
+        .bg(app.palette.accent)
+        .add_modifier(Modifier::BOLD);
+
+    let kb = &app.keybinds;
+    let line = Line::from(vec![
+        Span::styled(" NAVIGATE ", mode_style),
+        Span::raw(" "),
+        Span::styled("esc", key),
+        Span::styled(" back  ", dim),
+        Span::styled("↑↓", key),
+        Span::styled(" ws  ", dim),
+        Span::styled("⇥", key),
+        Span::styled(" pane  ", dim),
+        Span::styled(kb.new_tab_label.as_str(), key),
+        Span::styled(" new tab  ", dim),
+        Span::styled(kb.split_vertical_label.as_str(), key),
+        Span::styled(" split│  ", dim),
+        Span::styled(kb.split_horizontal_label.as_str(), key),
+        Span::styled(" split─  ", dim),
+        Span::styled(kb.close_pane_label.as_str(), key),
+        Span::styled(" close  ", dim),
+        Span::styled(kb.fullscreen_label.as_str(), key),
+        Span::styled(" full  ", dim),
+        Span::styled(kb.resize_mode_label.as_str(), key),
+        Span::styled(" resize  ", dim),
+        Span::styled("?", key),
+        Span::styled(" keybinds  ", dim),
+        Span::styled("s", key),
+        Span::styled(" settings  ", dim),
+        Span::styled("q", key),
+        Span::styled(" quit", dim),
+    ]);
+
+    let overlay_y = area.y + area.height.saturating_sub(1);
+    let overlay_area = Rect::new(area.x, overlay_y, area.width, 1);
+    render_bottom_bar(frame, overlay_area, line, app.palette.panel_bg);
+
+    if app.update_available.is_some() {
+        let status = Line::from(vec![Span::styled(
+            " update ready",
+            Style::default()
+                .fg(app.palette.accent)
+                .add_modifier(Modifier::BOLD),
+        )]);
+        let width = 13u16.min(overlay_area.width);
+        let status_area = Rect::new(
+            overlay_area.x + overlay_area.width.saturating_sub(width),
+            overlay_area.y,
+            width,
+            overlay_area.height,
+        );
+        frame.render_widget(Clear, status_area);
+        frame.render_widget(
+            Paragraph::new(status).alignment(Alignment::Right),
+            status_area,
+        );
+    }
+}
+
+pub(super) fn render_global_launcher_menu(app: &AppState, frame: &mut Frame) {
+    let rect = app.global_menu_rect();
+    let Some(inner) = render_panel_shell(frame, rect, app.palette.accent, app.palette.panel_bg)
+    else {
+        return;
+    };
+
+    let items = app.global_menu_labels();
+    for (idx, item) in items.iter().enumerate() {
+        let y = inner.y + idx as u16;
+        if y >= inner.y + inner.height {
+            break;
+        }
+        let selected = idx == app.global_menu.highlighted;
+        let rect = Rect::new(inner.x, y, inner.width, 1);
+
+        if *item == "update ready" {
+            let line = if selected {
+                Line::from(vec![
+                    Span::styled(
+                        " update ready ",
+                        Style::default()
+                            .fg(panel_contrast_fg(&app.palette))
+                            .bg(app.palette.accent)
+                            .add_modifier(Modifier::BOLD),
+                    ),
+                    Span::styled(
+                        "● ",
+                        Style::default()
+                            .fg(panel_contrast_fg(&app.palette))
+                            .bg(app.palette.accent)
+                            .add_modifier(Modifier::BOLD),
+                    ),
+                ])
+            } else {
+                Line::from(vec![
+                    Span::styled(" update ready ", Style::default().fg(app.palette.text)),
+                    Span::styled(
+                        "● ",
+                        Style::default()
+                            .fg(app.palette.accent)
+                            .add_modifier(Modifier::BOLD),
+                    ),
+                ])
+            };
+            frame.render_widget(Paragraph::new(line).alignment(Alignment::Left), rect);
+            continue;
+        }
+
+        let style = if selected {
+            Style::default()
+                .fg(panel_contrast_fg(&app.palette))
+                .bg(app.palette.accent)
+                .add_modifier(Modifier::BOLD)
+        } else {
+            Style::default().fg(app.palette.text)
+        };
+        frame.render_widget(
+            Paragraph::new(format!(" {item} "))
+                .style(style)
+                .alignment(Alignment::Left),
+            rect,
+        );
+    }
+}
+
+pub(super) fn render_resize_overlay(app: &AppState, frame: &mut Frame, area: Rect) {
+    let key = Style::default()
+        .fg(app.palette.accent)
+        .add_modifier(Modifier::BOLD);
+    let dim = Style::default().fg(app.palette.overlay0);
+
+    let mode_style = Style::default()
+        .fg(panel_contrast_fg(&app.palette))
+        .bg(app.palette.mauve)
+        .add_modifier(Modifier::BOLD);
+
+    let line = Line::from(vec![
+        Span::styled(" RESIZE ", mode_style),
+        Span::raw("  "),
+        Span::styled("h/l", key),
+        Span::styled(" width  ", dim),
+        Span::styled("j/k", key),
+        Span::styled(" height  ", dim),
+        Span::styled("esc", key),
+        Span::styled(" done", dim),
+    ]);
+
+    let overlay_y = area.y + area.height.saturating_sub(1);
+    let overlay_area = Rect::new(area.x, overlay_y, area.width, 1);
+    render_bottom_bar(frame, overlay_area, line, app.palette.panel_bg);
+}
+
+pub(super) fn render_context_menu(app: &AppState, frame: &mut Frame) {
+    let Some(menu) = &app.context_menu else {
+        return;
+    };
+
+    let p = &app.palette;
+    let Some(menu_rect) = app.context_menu_rect() else {
+        return;
+    };
+    let Some(inner) = render_panel_shell(frame, menu_rect, p.accent, p.panel_bg) else {
+        return;
+    };
+
+    let items: Vec<ListItem> = menu
+        .items()
+        .iter()
+        .map(|item| ListItem::new(Line::from(*item)))
+        .collect();
+    let list = List::new(items)
+        .style(Style::default().fg(p.text))
+        .highlight_style(
+            Style::default()
+                .bg(p.accent)
+                .fg(panel_contrast_fg(p))
+                .add_modifier(Modifier::BOLD),
+        )
+        .highlight_symbol(" ");
+    let mut state = ListState::default().with_selected(Some(menu.list.highlighted));
+    frame.render_stateful_widget(list, inner, &mut state);
+}