fix: fit the detail pane's subject and metadata lines to the plate

The detail pane's subject header, From, To and Date lines rode the
boundless label drain with no width budget, so a long subject ran
straight off the right edge of the message plate. They are now
ellipsized to the pane's text column by estimated width and clipped to
the plate's content rect as the backstop for the estimate.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

 src/main.rs | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 73 insertions(+), 13 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 9cbc4e2..96547ae 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1155,6 +1155,34 @@ fn ellipsize(s: &str, max_chars: usize) -> String {
     }
 }
 
+/// Ellipsize `s` so its estimated rendered width at `font_size` fits in
+/// `max_w` px. [`ellipsize`] budgets by CHARACTER count, which is fine for
+/// list rows that are also clipped to their viewport, but the detail pane's
+/// header lines were emitted with no bounds and no budget at all, so a long
+/// subject ran straight off the plate. The estimate is the same heuristic the
+/// date column and the empty-pane placeholder already lay out by; callers
+/// still clip at the plate edge so an under-estimate is cut, not overflowed.
+fn ellipsize_to_width(s: &str, font_size: f32, max_w: f32) -> String {
+    if TextLabel::estimate_width(s, font_size) <= max_w {
+        return s.to_string();
+    }
+    let chars: Vec<char> = s.chars().collect();
+    // Largest prefix whose width, plus the ellipsis, still fits. Widths are
+    // monotone in prefix length, so a binary search over the count is exact.
+    let (mut lo, mut hi) = (0usize, chars.len());
+    while lo < hi {
+        let mid = (lo + hi).div_ceil(2);
+        let candidate: String = chars[..mid].iter().collect::<String>() + "...";
+        if TextLabel::estimate_width(&candidate, font_size) <= max_w {
+            lo = mid;
+        } else {
+            hi = mid - 1;
+        }
+    }
+    let head: String = chars[..lo].iter().collect();
+    format!("{}...", head.trim_end())
+}
+
 /// Display form of the From address: "Name <addr>", falling back through the
 /// parts. mail-parser has already decoded any RFC 2047 encoded-words.
 fn format_from(msg: &mail_parser::Message) -> String {
@@ -3831,19 +3859,36 @@ impl ClearEmailApp {
         if modal_open {
         } else if let Some(selected_id) = self.selected_email_id {
             if let Some(email) = self.emails.iter().find(|e| e.id == selected_id) {
-                // Subject Header
-                labels.push(TextLabel {
-                    text: email.subject.clone(),
-                    x: detail_x,
-                    y: self.detail_origin_y() + DETAIL_SUBJECT_Y,
-                    font_size: 15.0,
-                    color: [0xff, 0xff, 0xff],
-                });
-
-                // Metadata
-                labels.push(TextLabel { text: format!("From: {}", email.from), x: detail_x, y: self.detail_origin_y() + DETAIL_FROM_Y, font_size: 11.0, color: [0xb0, 0xb0, 0xb8] });
-                labels.push(TextLabel { text: format!("To:   {}", email.to), x: detail_x, y: self.detail_origin_y() + DETAIL_TO_Y, font_size: 11.0, color: [0x83, 0x83, 0x8a] });
-                labels.push(TextLabel { text: format!("Date: {}", email.date), x: detail_x, y: self.detail_origin_y() + DETAIL_DATE_Y, font_size: 11.0, color: [0x83, 0x83, 0x8a] });
+                // Subject header and metadata lines: single-line, so a long
+                // subject (or address list) is ellipsized to the pane's text
+                // column, and the label is clipped to the plate's content rect
+                // as the backstop for the width estimate — these used to ride
+                // the boundless `labels` drain and ran off the plate.
+                let content_w = self.detail_content_w();
+                let (plate_x, plate_y, plate_w, plate_h) = self.detail_pane_geom();
+                let header_bounds = Some([
+                    plate_x + pane_inner_pad(),
+                    plate_y,
+                    plate_x + plate_w - pane_inner_pad(),
+                    plate_y + plate_h,
+                ]);
+                let header_lines: [(String, f32, f32, [u8; 3]); 4] = [
+                    (email.subject.clone(), DETAIL_SUBJECT_Y, 15.0, [0xff, 0xff, 0xff]),
+                    (format!("From: {}", email.from), DETAIL_FROM_Y, 11.0, [0xb0, 0xb0, 0xb8]),
+                    (format!("To:   {}", email.to), DETAIL_TO_Y, 11.0, [0x83, 0x83, 0x8a]),
+                    (format!("Date: {}", email.date), DETAIL_DATE_Y, 11.0, [0x83, 0x83, 0x8a]),
+                ];
+                for (text, dy, font_size, color) in header_lines {
+                    pc.text_with(
+                        ellipsize_to_width(&text, font_size, content_w),
+                        detail_x,
+                        self.detail_origin_y() + dy,
+                        font_size,
+                        color,
+                        None,
+                        header_bounds,
+                    );
+                }
 
                 // Server-attachment chip labels (quads paint in display_list;
                 // both sides lay out via detail_chip_rects).
@@ -6217,6 +6262,21 @@ fn main() {
 
 #[cfg(test)]
 mod tests {
+    #[test]
+    fn ellipsize_to_width_fits_the_column() {
+        let long = "Re: A very long subject line that certainly will not fit in a narrow detail pane column";
+        let fitted = ellipsize_to_width(long, 15.0, 200.0);
+        assert!(fitted.ends_with("..."));
+        assert!(TextLabel::estimate_width(&fitted, 15.0) <= 200.0, "{fitted}");
+        // One more char would not have fit: the prefix is maximal.
+        let head_len = fitted.trim_end_matches("...").chars().count();
+        let longer: String = long.chars().take(head_len + 2).collect::<String>() + "...";
+        assert!(TextLabel::estimate_width(&longer, 15.0) > 200.0);
+        // Short text is untouched, and a hopeless width degrades to the ellipsis alone.
+        assert_eq!(ellipsize_to_width("Hi", 15.0, 200.0), "Hi");
+        assert_eq!(ellipsize_to_width("Hello world", 15.0, 1.0), "...");
+    }
+
     use super::*;
 
     #[test]