fix(nbd): change graph repeat-node marker from [cycle] to * [8b4041]

The [cycle] label was misleading — a node marked this way is not
necessarily in a true cycle, it is simply a shared dependency appearing
in multiple branches of the tree. The `*` marker is more neutral and
concise.

Changes: render_node in display.rs, test in tests.rs, README.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nbd/README.md

@@ -155,7 +155,7 @@ a3f9c2  [done]  Fix login bug
 └── d1f302  [done]  Update docs
 ```
 
-When a ticket appears in multiple subtrees it is rendered as `[cycle]` on its
+When a ticket appears in multiple subtrees it is rendered as `*` on its
 second occurrence to keep the output finite. Edges in JSON output use
 `{"from": <blocker>, "to": <blocked>}` — the blocking ticket is `from`.
 

nbd/src/display.rs

@@ -360,7 +360,8 @@ pub fn print_diff(old: &Ticket, new: &Ticket) {
 /// e4a781  [todo]  New feature (no deps)
 /// ```
 ///
-/// Cycles are detected and labelled `[cycle]` rather than looping forever.
+/// Nodes that appear in multiple subtrees are marked `*` on subsequent
+/// occurrences rather than looping forever.
 pub fn format_graph(graph: &TicketGraph<'_>) -> String {
     let mut out = String::new();
     let mut visited: HashSet<String> = HashSet::new();
@@ -408,8 +409,8 @@ pub fn print_subtree(graph: &TicketGraph<'_>, root_id: &str) {
 ///   becomes their `prefix`). It accumulates one more level of `│   ` or
 ///   `    ` with each descent.
 ///
-/// When a node ID is already in `visited`, it is rendered as `[cycle]` and
-/// the recursion stops, preventing infinite loops in cyclic data.
+/// When a node ID is already in `visited`, it is rendered as `*` and
+/// the recursion stops, preventing infinite loops in cyclic or shared data.
 fn render_node(
     graph: &TicketGraph<'_>,
     id: &str,
@@ -419,9 +420,9 @@ fn render_node(
     visited: &mut HashSet<String>,
     out: &mut String,
 ) {
-    // Cycle detection.
+    // Already-visited detection: this node appears elsewhere in the tree.
     if visited.contains(id) {
-        append_line(out, &format!("{prefix}{connector}{id}  [cycle]"));
+        append_line(out, &format!("{prefix}{connector}{id}  *"));
         return;
     }
     visited.insert(id.to_string());

nbd/src/tests.rs

@@ -1315,7 +1315,7 @@ mod display_graph {
         assert!(format_subtree(&graph, "ffffff").is_empty());
     }
 
-    /// When the data contains a cycle, the repeated node is labelled `[cycle]`
+    /// When the data contains a cycle, the repeated node is marked with `*`
     /// and the output is finite (no infinite loop).
     ///
     /// A pure cycle (A depends on B, B depends on A) has no roots, so we use
@@ -1329,9 +1329,12 @@ mod display_graph {
         let tickets = vec![a, b];
         let graph = TicketGraph::build(&tickets);
         // format_subtree drives rendering from "aaaaaa"; when it tries to
-        // revisit "aaaaaa" via bbbbbb's dependent edge, it should hit [cycle].
+        // revisit "aaaaaa" via bbbbbb's dependent edge, it should mark with *.
         let out = format_subtree(&graph, "aaaaaa");
-        assert!(out.contains("[cycle]"), "cycle should be labelled: {out}");
+        assert!(
+            out.contains(" *"),
+            "repeated node should be marked with *: {out}"
+        );
     }
 
     /// An empty graph renders as an empty string.