feat(quick-1): add arrow key navigation and directory descriptions

- Add bare Left arrow key as alias for navigate_back (same as Backspace)
- Add bare Right arrow key as alias for navigate_forward (same as Alt+Right)
- Update handle_key doc comment to list new Left/Right bindings
- Add description field to DirEntry struct in vault.rs
- Add extract_frontmatter_description() to parse YAML frontmatter
- Populate description from frontmatter in list_vault_files()
- Show descriptions in DarkGray beside file entries in build_directory_lines()
- Truncate descriptions to keep total line width within 78 chars
- Link span_len covers only [name] portion, not the description

src/app.rs

@@ -450,6 +450,8 @@ impl App {
     /// - `Backspace`    — navigate back in history
     /// - `Alt+Left`     — navigate back in history
     /// - `Alt+Right`    — navigate forward in history
+    /// - `Left`         — navigate back in history (same as Backspace)
+    /// - `Right`        — navigate forward in history (same as Alt+Right)
     /// - `j` / `Down`   — scroll down one line
     /// - `k` / `Up`     — scroll up one line
     /// - `PgDn`         — scroll down one page
@@ -498,6 +500,13 @@ impl App {
             KeyCode::Right if key.modifiers.contains(KeyModifiers::ALT) => {
                 self.navigate_forward();
             }
+            // Bare Left/Right arrows also navigate back/forward
+            KeyCode::Left => {
+                self.navigate_back();
+            }
+            KeyCode::Right => {
+                self.navigate_forward();
+            }
             // ── Scrolling keys — do NOT dismiss the quit prompt ───────────────
             KeyCode::Char('j') | KeyCode::Down => {
                 self.scroll_down(1);
@@ -1362,13 +1371,40 @@ fn build_directory_lines(
             let span_len = display.chars().count();
             let line_index = lines.len(); // This line's index in the lines vec
 
-            lines.push(Line::from(vec![
+            // Build spans: indent + [name] + optional description in DarkGray
+            let mut spans = vec![
                 Span::raw(indent),
-                Span::styled(
+                Span::styled(display.clone(), Style::default().fg(Color::LightCyan)),
-                    display,
+            ];
-                    Style::default().fg(Color::LightCyan),
+
-                ),
+            if let Some(ref desc) = entry.description {
-            ]));
+                // Truncate description so total line width stays within ~78 chars
+                // Total used: indent_chars + span_len + 2 (separator) + desc
+                let budget = 78usize
+                    .saturating_sub(indent_chars)
+                    .saturating_sub(span_len)
+                    .saturating_sub(2); // 2 spaces separator
+                let truncated = if desc.chars().count() > budget {
+                    if budget > 3 {
+                        let trimmed: String = desc.chars().take(budget - 3).collect();
+                        format!("{}...", trimmed)
+                    } else {
+                        String::new()
+                    }
+                } else {
+                    desc.clone()
+                };
+
+                if !truncated.is_empty() {
+                    spans.push(Span::raw("  "));
+                    spans.push(Span::styled(
+                        truncated,
+                        Style::default().fg(Color::DarkGray),
+                    ));
+                }
+            }
+
+            lines.push(Line::from(spans));
 
             link_records.push(crate::renderer::LinkRecord {
                 line_index,

src/vault.rs

@@ -1,4 +1,4 @@
-use std::io;
+use std::io::{self, BufRead};
 use std::path::{Path, PathBuf};
 use walkdir::WalkDir;
 
@@ -201,6 +201,62 @@ pub struct DirEntry {
     pub is_dir: bool,
     /// Vault-relative path (only for .md files; None for directories).
     pub vault_path: Option<String>,
+    /// Short description from the file's YAML frontmatter `description:` field.
+    /// None if the file has no frontmatter or no description key.
+    pub description: Option<String>,
+}
+
+// ── Frontmatter parsing ───────────────────────────────────────────────────────
+
+/// Extract the `description` value from a YAML frontmatter block at the top of a file.
+///
+/// Reads only the first 20 lines to avoid loading large files entirely.
+/// The frontmatter must start with `---` on the first line and be closed by
+/// another `---` line. The `description:` key is matched case-sensitively.
+///
+/// Handles both bare values (`description: some text`) and quoted values
+/// (`description: "some text"`).
+///
+/// Returns `Some(description)` if found, `None` otherwise.
+fn extract_frontmatter_description(path: &Path) -> Option<String> {
+    let file = std::fs::File::open(path).ok()?;
+    let reader = io::BufReader::new(file);
+
+    let mut lines = reader.lines().take(20);
+
+    // First line must be exactly "---"
+    let first = lines.next()?.ok()?;
+    if first.trim() != "---" {
+        return None;
+    }
+
+    // Scan remaining lines for description key, stop at closing "---"
+    for line in lines {
+        let line = line.ok()?;
+        let trimmed = line.trim();
+
+        if trimmed == "---" {
+            // End of frontmatter — description not found
+            break;
+        }
+
+        if let Some(rest) = trimmed.strip_prefix("description:") {
+            let value = rest.trim();
+            // Strip surrounding quotes if present
+            let value = if (value.starts_with('"') && value.ends_with('"'))
+                || (value.starts_with('\'') && value.ends_with('\''))
+            {
+                &value[1..value.len() - 1]
+            } else {
+                value
+            };
+            if !value.is_empty() {
+                return Some(value.to_string());
+            }
+        }
+    }
+
+    None
 }
 
 /// List all markdown files and directories in the vault, sorted alphabetically.
@@ -231,6 +287,7 @@ pub fn list_vault_files(vault_path: &Path) -> Vec<DirEntry> {
                 name,
                 is_dir: true,
                 vault_path: None,
+                description: None,
             });
         } else if name.ends_with(".md") {
             let display_name = name.strip_suffix(".md").unwrap_or(&name).to_string();
@@ -240,11 +297,13 @@ pub fn list_vault_files(vault_path: &Path) -> Vec<DirEntry> {
                 .unwrap_or(entry.path())
                 .to_string_lossy()
                 .to_string();
+            let description = extract_frontmatter_description(entry.path());
             entries.push(DirEntry {
                 depth,
                 name: display_name,
                 is_dir: false,
                 vault_path: Some(rel),
+                description,
             });
         }
         // Skip non-.md files silently