fix: 3 bugs from peer code review

- justify: gate DIM/RESET separator coloring on color_enabled param;
  previously leaked ANSI escapes when --color=never or NO_COLOR was set
- vcs: apply branch name truncation per config (truncate.enabled,
  truncate.max, truncate.style) for both git and jj renderers;
  previously ignored truncate config causing long branch names to
  overflow and trigger unnecessary priority drops
- flex: account for prefix/suffix overhead when computing context_bar
  flex expansion width; previously double-applied apply_formatting
  causing line to overshoot term_width when prefix/suffix configured

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

src/layout/flex.rs

@@ -44,12 +44,14 @@ pub fn flex_expand(active: &mut [ActiveSection], ctx: &RenderContext, separator:
             ansi: padding,
         };
     } else if active[idx].id == "context_bar" {
-        // Rebuild context_bar with wider bar_width
+        // Rebuild context_bar with wider bar_width.
+        // Account for prefix/suffix that apply_formatting will add,
+        // so the final width doesn't overshoot term_width.
+        let base = &ctx.config.sections.context_bar.base;
+        let fmt_overhead = formatting_overhead(base);
         let cur_bar_width = ctx.config.sections.context_bar.bar_width;
-        let new_bar_width = cur_bar_width + extra as u16;
+        let new_bar_width = cur_bar_width + extra.saturating_sub(fmt_overhead) as u16;
         if let Some(mut output) = section::context_bar::render_at_width(ctx, new_bar_width) {
-            // Re-apply formatting after flex rebuild
-            let base = &ctx.config.sections.context_bar.base;
             format::apply_formatting(
                 &mut output.raw,
                 &mut output.ansi,
@@ -66,6 +68,13 @@ pub fn flex_expand(active: &mut [ActiveSection], ctx: &RenderContext, separator:
     }
 }
 
+/// Calculate display width of prefix + suffix that apply_formatting will add.
+fn formatting_overhead(base: &crate::config::SectionBase) -> usize {
+    let pfx = base.prefix.as_deref().map_or(0, format::display_width);
+    let sfx = base.suffix.as_deref().map_or(0, format::display_width);
+    pfx + sfx
+}
+
 fn line_width(active: &[ActiveSection], separator: &str) -> usize {
     let sep_w = format::display_width(separator);
     let mut total = 0;

src/layout/justify.rs

@@ -10,6 +10,7 @@ pub fn justify(
     term_width: u16,
     separator: &str,
     _mode: JustifyMode,
+    color_enabled: bool,
 ) -> String {
     let content_width: usize = active
         .iter()
@@ -37,11 +38,15 @@ pub fn justify(
         if i > 0 {
             let this_gap = gap_width + usize::from(i - 1 < gap_remainder);
             let gap_str = build_gap(sep_core, sep_core_len, this_gap);
-            output.push_str(&format!(
-                "{}{gap_str}{}",
-                crate::color::DIM,
-                crate::color::RESET
-            ));
+            if color_enabled {
+                output.push_str(&format!(
+                    "{}{gap_str}{}",
+                    crate::color::DIM,
+                    crate::color::RESET
+                ));
+            } else {
+                output.push_str(&gap_str);
+            }
         }
         output.push_str(&sec.output.ansi);
     }

src/layout/mod.rs

@@ -109,6 +109,7 @@ fn render_line(section_ids: &[String], ctx: &RenderContext, separator: &str) ->
             ctx.term_width,
             separator,
             ctx.config.global.justify,
+            ctx.color_enabled,
         )
     } else {
         flex::flex_expand(&mut active, ctx, separator);

src/section/vcs.rs

@@ -82,7 +82,13 @@ fn render_git(
         }
     };
 
-    let branch = status.branch.as_deref().unwrap_or("?");
+    let branch_raw = status.branch.as_deref().unwrap_or("?");
+    let trunc = &ctx.config.sections.vcs.truncate;
+    let branch = if trunc.enabled && trunc.max > 0 {
+        crate::format::truncate(branch_raw, trunc.max, &trunc.style)
+    } else {
+        branch_raw.to_string()
+    };
     let branch_glyph = glyph::glyph("branch", glyphs);
     let dirty_glyph = if status.is_dirty && ctx.config.sections.vcs.show_dirty {
         glyph::glyph("dirty", glyphs)
@@ -154,6 +160,13 @@ fn render_jj(
         Some(out)
     })?;
 
+    let trunc = &ctx.config.sections.vcs.truncate;
+    let branch = if trunc.enabled && trunc.max > 0 {
+        crate::format::truncate(&branch, trunc.max, &trunc.style)
+    } else {
+        branch
+    };
+
     let branch_glyph = glyph::glyph("branch", glyphs);
     let raw = format!("{branch_glyph}{branch}");
     let ansi = if ctx.color_enabled {