Parse per-file Word Count Target header and show progress

Header parsing now recognises a `Word Count Target:` line at any heading
level (## included) in addition to `# Title:`/`# Slug:`, and accepts one
or more leading `#`. The value parses a single number or a range —
"1500 - 2000", "1500-2000", "1,500 to 2,000" — into a min/max WordGoal
(stripped from the exported document like the other header lines).

When a target is set, the status bar shows a progress bar of the file's
prose word count (the body below the draft marker) against it: amber
under the target, green in range, blue over. Aliases "Word Count Goal:"
and "Word Count:" also work.

Adds preprocess tests for the range forms, ## heading level, alias, and
absence; 44 tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N9kRuP7JvXoUGdNNeg5ZSs

src/app.rs

@@ -523,6 +523,16 @@ impl App {
         resolve_chapter_title(None, header.title.as_deref(), idx, self.index_pad_width())
     }
 
+    /// The current file's word-count target (from its `Word Count Target:`
+    /// header) paired with its current prose word count, if a target is set.
+    /// Prose = the body below the draft marker, so header metadata isn't counted.
+    fn current_goal(&self) -> Option<(crate::preprocess::WordGoal, usize)> {
+        self.selected?;
+        let header = crate::preprocess::parse(&self.buffer, &self.config.draft_marker);
+        let goal = header.goal?;
+        Some((goal, count_words(&header.body)))
+    }
+
     fn export_odt(&mut self) {
         self.save_current();
         let marker = self.config.draft_marker.clone();
@@ -1205,6 +1215,7 @@ impl App {
                 let dirty = if self.dirty { " • unsaved" } else { "" };
                 ui.label(format!("{}{dirty}", self.status));
 
+                let goal = self.current_goal();
                 ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
                     if let Some(idx) = self.selected {
                         let name = &self.files[idx];
@@ -1224,6 +1235,23 @@ impl App {
                         .on_hover_text(
                             "Words in the current file · net change since this session opened",
                         );
+
+                        // Progress toward the file's Word Count Target, if set.
+                        if let Some((goal, prose)) = goal {
+                            let (frac, color, text) = goal_progress(goal, prose);
+                            ui.separator();
+                            ui.add(
+                                egui::ProgressBar::new(frac)
+                                    .desired_width(150.0)
+                                    .fill(color)
+                                    .text(egui::RichText::new(text).small()),
+                            )
+                            .on_hover_text(
+                                "Prose words vs the file's “Word Count Target” header \
+                                 (counts the body below the draft marker). Amber = under \
+                                 target, green = in range, blue = over.",
+                            );
+                        }
                     }
                 });
             });
@@ -2564,6 +2592,30 @@ fn count_words(s: &str) -> usize {
     s.split_whitespace().count()
 }
 
+/// Progress toward a word-count target: the bar fraction (0..=1), a fill colour
+/// (amber under the range, green within it, blue over it), and a label like
+/// "1,234 / 1,500–2,000".
+fn goal_progress(goal: crate::preprocess::WordGoal, prose: usize) -> (f32, egui::Color32, String) {
+    let frac = if goal.max == 0 {
+        0.0
+    } else {
+        (prose as f32 / goal.max as f32).clamp(0.0, 1.0)
+    };
+    let color = if prose < goal.min {
+        egui::Color32::from_rgb(0xC8, 0x8A, 0x2A) // amber: below target
+    } else if prose <= goal.max {
+        egui::Color32::from_rgb(0x3F, 0x9E, 0x4F) // green: in range
+    } else {
+        egui::Color32::from_rgb(0x3B, 0x82, 0xF6) // blue: over target
+    };
+    let target = if goal.min == goal.max {
+        thousands(goal.max)
+    } else {
+        format!("{}–{}", thousands(goal.min), thousands(goal.max))
+    };
+    (frac, color, format!("{} / {}", thousands(prose), target))
+}
+
 /// Format a non-negative integer with comma thousands separators (e.g. 12345 -> "12,345").
 fn thousands(n: usize) -> String {
     let digits = n.to_string();