Add status column to context tree with tab-stop alignment

SectionView gains a status field for extra info displayed after the
token count column. Memory nodes section shows "N scored, M unscored"
in the status column instead of burying it in the title.

Renderer uses fixed-width columns (40 name, 16 tokens, status) for
consistent alignment across sections.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/user/widgets.rs

@@ -18,6 +18,8 @@ pub struct SectionView {
     pub tokens: usize,
     pub content: String,
     pub children: Vec<SectionView>,
+    /// Extra status text shown after the token count.
+    pub status: String,
 }
 
 /// Build a SectionView tree from a ContextSection.
@@ -34,6 +36,7 @@ pub fn section_to_view(section: &ContextSection) -> SectionView {
             tokens: ce.tokens,
             content,
             children: Vec::new(),
+            status: String::new(),
         }
     }).collect();
     SectionView {
@@ -41,6 +44,7 @@ pub fn section_to_view(section: &ContextSection) -> SectionView {
         tokens: section.tokens(),
         content: String::new(),
         children,
+        status: String::new(),
     }
 }
 
@@ -244,7 +248,13 @@ impl SectionTree {
 
         let indent = "  ".repeat(depth + 1);
         let marker = if !expandable { " " } else if expanded { "▼" } else { "▶" };
-        let label = format!("{}{} {:30} {:>6} tokens", indent, marker, section.name, section.tokens);
+        let name_col = format!("{}{} {}", indent, marker, section.name);
+        let tokens_col = format!("{:>6} tokens", section.tokens);
+        let label = if section.status.is_empty() {
+            format!("{:40} {}", name_col, tokens_col)
+        } else {
+            format!("{:40} {:16} {}", name_col, tokens_col, section.status)
+        };
         let style = if selected {
             Style::default().fg(Color::Yellow).add_modifier(Modifier::BOLD)
         } else {