Add connect mode, portals, backlinks and renames (stage 8d, v1)

Part 8d, the last of stage 8, and with it everything on DESIGN.md's v1
list.

Connect mode (C): the cursor goes to another node, a dashed arrow in the
visual color follows it, and Enter links the two; then the cursor goes
back to where C was typed (the user's pick). d removes the line between
them (a branch is cut, and the child comes loose), > puts the node under
the other one, and <Space> a, l, c, s and t style the line as you watch,
making it when it isn't there yet. Everything connect mode changes is one
undo group, and Esc takes it back with History::cancel, which leaves
nothing to redo. From visual mode every selected node connects, and the
line pickers go back to connect mode when they close.

Portals show their document live, from a cache of what each document
file holds (open documents from their buffers, the others from their
files, looked at every second): the root's title, its color and how many
nodes it has, or ? when the document isn't there. Enter or gf goes
through, as a jump, and the pane's breadcrumb starts with the documents
it came through. <Space>p types :portal (the user's pick): a path as :e
takes it, or the title of a new document. Backlinks are put right
whenever a document is opened or saved; the root shows how many, the
Note view lists them, gu goes up to them (the user's pick) and
:backlinks lists them.

File names follow the root's title: when it changed, the next save
renames the file (-2 when the name is taken; a folder's default document
keeps its name), and the portals pointing at it, its backlinks in the
documents it leads to, the recent documents, the capital marks and the
jump lists follow. A portal whose file was moved by hand finds its
document in that folder by uid. Portals in a register keep full paths,
so a pasted portal leads to the same document from any folder.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/view/outline.rs

@@ -35,6 +35,7 @@ use unicode_width::UnicodeWidthStr;
 
 use crate::app::action::{Action, AppAction, Message};
 use crate::app::commands;
+use crate::app::connect;
 use crate::app::mode::Mode;
 use crate::app::popup::MenuFor;
 use crate::app::text_edit::{EditAt, StartEdit, TextEdit};
@@ -124,6 +125,7 @@ impl OutlineView {
         let edit = ctx.mode.title_edit();
         self.picked = match ctx.mode {
             Mode::Visual(visual) => selection(visual, ctx, ViewKind::Outline).into_iter().collect(),
+            Mode::Connect(connecting) => connect::others(connecting, ctx.cursor).into_iter().collect(),
             _ => BTreeSet::new(),
         };
         // The color of the lines from a node to its children, as on the
@@ -173,7 +175,7 @@ impl OutlineView {
         let (doc, theme, glyphs) = (ctx.doc, ctx.theme, ctx.theme.glyphs);
         let Some(node) = doc.node(id) else { return };
         let top_level = lines.spans.is_empty();
-        let style = theme.node_style(node, id == doc.root());
+        let style = ctx.node_style(id, node);
         let color = style.color;
         let has_children = !doc.children(id).is_empty();
         let folded = visible.hidden.contains_key(&id);
@@ -228,6 +230,9 @@ impl OutlineView {
         if has_body && !self.bodies {
             lines.push(format!(" {}", glyphs.body_mark()), muted);
         }
+        if let Some(badge) = ctx.badge(id, node) {
+            lines.push(format!("  {badge}"), muted);
+        }
         if let Some(count) = visible.hidden.get(&id) {
             lines.push(format!("  +{count}"), muted);
         }
@@ -433,6 +438,7 @@ impl View for OutlineView {
             mode,
             &[Context::Outline, Context::Normal, Context::Motions],
             &[Context::Visual, Context::Outline, Context::Motions],
+            &[Context::Connect, Context::Outline, Context::Motions],
         )
     }
 
@@ -475,7 +481,7 @@ impl View for OutlineView {
     fn command(&mut self, typed: &Typed, ctx: &ViewContext<'_>) -> Option<Vec<Action>> {
         match ctx.mode {
             Mode::Move(grab) => return commands::reorder(typed, grab, ctx),
-            Mode::Normal | Mode::Visual(_) => {}
+            Mode::Normal | Mode::Visual(_) | Mode::Connect(_) => {}
             Mode::Text(_) | Mode::Command(_) | Mode::Popup(_) => return None,
         }
         let rows = isize::try_from(typed.times()).unwrap_or(1);