feat: Implement bidirectional Story Bible links with draft text

- Add story_bible.rs module with StoryBibleIndex, StoryBibleItem, and
  StoryBibleReference types for indexing Story Bible content
- Support wiki-style [[...]] and mention-style @... syntax for references
- Highlight Story Bible references in editor with purple background
- Add Story Bible window (View > Tools > Story Bible) to browse items
- Show references from current draft file in Story Bible window
- Allow clicking references to jump to their location in the editor
- Auto-index Story Bible items from common directories (03-Characters,
  02-Story Bible, Characters, etc.)
- Extract metadata from YAML frontmatter or filenames
- Add walkdir dependency for directory scanning
- Fix pre-existing format string errors in workspace.rs

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

src/app/editor.rs

@@ -43,6 +43,13 @@ impl App {
             .id_salt("editor")
             .auto_shrink([false, false])
             .show(ui, |ui| {
+                // Prepare Story Bible reference ranges for highlighting
+                let bible_ranges: Vec<(usize, usize)> = self
+                    .current_references
+                    .iter()
+                    .map(|r| (r.column, r.column + r.length))
+                    .collect();
+                
                 let mut layouter = move |ui: &egui::Ui, text: &str, wrap_width: f32| {
                     let job = build_editor_job(
                         text,
@@ -51,6 +58,7 @@ impl App {
                         &ranges,
                         &find_ranges,
                         find_active,
+                        &bible_ranges,
                         wrap_width,
                     );
                     ui.fonts(|f| f.layout_job(job))
@@ -105,6 +113,8 @@ impl App {
                     self.find_needs_refresh = true;
                     self.spell_dirty = true;
                     self.spell_last_edit = Some(Instant::now());
+                    // Update Story Bible references for the current file
+                    self.update_current_references();
                 }
                 // Markdown formatting hotkeys, applied to the current selection
                 // while the editor is focused (Ctrl/Cmd + B / I / E / K, and
@@ -358,6 +368,7 @@ impl App {
 /// get a red underline, grammar/style issues a blue one. `find` are
 /// `(start_byte, end_byte)` search-match ranges, shaded with a translucent
 /// highlight; the one at index `find_active` (if any) is shaded more strongly.
+/// `bible` are Story Bible reference ranges, highlighted with a distinctive color.
 pub(super) fn build_editor_job(
     text: &str,
     size: f32,
@@ -365,6 +376,7 @@ pub(super) fn build_editor_job(
     grammar: &[(usize, usize, bool)],
     find: &[(usize, usize)],
     find_active: Option<usize>,
+    bible: &[(usize, usize)],
     wrap_width: f32,
 ) -> egui::text::LayoutJob {
     use egui::text::{LayoutJob, TextFormat};
@@ -377,7 +389,7 @@ pub(super) fn build_editor_job(
         return job;
     }
 
-    // Split the text at every match boundary (grammar and find), then format
+    // Split the text at every match boundary (grammar, find, and bible), then format
     // each run according to which ranges cover it.
     let mut points: Vec<usize> = vec![0, text.len()];
     for &(s, e, _) in grammar {
@@ -388,6 +400,10 @@ pub(super) fn build_editor_job(
         points.push(s);
         points.push(e);
     }
+    for &(s, e) in bible {
+        points.push(s);
+        points.push(e);
+    }
     points.retain(|&p| p <= text.len() && text.is_char_boundary(p));
     points.sort_unstable();
     points.dedup();
@@ -397,6 +413,8 @@ pub(super) fn build_editor_job(
     // Translucent so the highlight reads in both light and dark themes.
     let find_bg = egui::Color32::from_rgba_unmultiplied(255, 213, 0, 70);
     let find_active_bg = egui::Color32::from_rgba_unmultiplied(255, 145, 0, 150);
+    // Story Bible reference highlight - purple/blue color
+    let bible_bg = egui::Color32::from_rgba_unmultiplied(138, 43, 226, 70);
     let width = (size * 0.08).max(1.5);
 
     for w in points.windows(2) {
@@ -421,6 +439,12 @@ pub(super) fn build_editor_job(
                 find_bg
             };
         }
+        // Check for Story Bible references and apply background highlight
+        // Only apply if not already highlighted by find
+        let is_find_highlight = find.iter().any(|&(s, e)| s < e && a >= s && b <= e);
+        if !is_find_highlight && bible.iter().any(|&(s, e)| s < e && a >= s && b <= e) {
+            fmt.background = bible_bg;
+        }
         job.append(&text[a..b], 0.0, fmt);
     }
     job
@@ -825,3 +849,19 @@ mod tests {
         assert_eq!(&text[char_to_byte(&text, sel.start)..char_to_byte(&text, sel.end)], "word");
     }
 }
+
+impl App {
+    /// Update the current_references list with Story Bible references found in the buffer.
+    pub(super) fn update_current_references(&mut self) {
+        if let Some(idx) = self.selected {
+            let file_path = self.files[idx].clone();
+            let mut refs = crate::story_bible::find_references(&self.buffer, &self.story_bible_index);
+            for r in refs.iter_mut() {
+                r.file_path = file_path.clone();
+            }
+            self.current_references = refs;
+        } else {
+            self.current_references.clear();
+        }
+    }
+}