Include the POV field in the file-list hover tooltip

Header parsing now also lifts a `POV:` line (any heading level). The
file-list tooltip combines it with the slug — "POV: <name>" then the
slug synopsis — cached per file alongside the slug (HoverInfo) and read
live from the buffer for the selected file. Adds a POV parse test.

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

src/preprocess.rs

@@ -29,6 +29,8 @@ pub struct Header {
     pub title: Option<String>,
     /// Value of the `# Slug:` line, if present and non-empty.
     pub slug: Option<String>,
+    /// Value of the `POV:` line, if present and non-empty.
+    pub pov: Option<String>,
     /// Word-count target from a `Word Count Target:` line, if present and parsable.
     pub goal: Option<WordGoal>,
     /// The prose body, with comments, the header block, and metadata lines removed.
@@ -39,6 +41,7 @@ pub struct Header {
 enum Meta {
     Title,
     Slug,
+    Pov,
     WordCount,
 }
 
@@ -105,6 +108,7 @@ fn meta_line(line: &str) -> Option<(Meta, String)> {
     for (key, meta) in [
         ("title:", Meta::Title),
         ("slug:", Meta::Slug),
+        ("pov:", Meta::Pov),
         ("word count target:", Meta::WordCount),
         ("word count goal:", Meta::WordCount),
         ("word count:", Meta::WordCount),
@@ -134,10 +138,12 @@ pub fn parse(markdown: &str, marker: &str) -> Header {
 
     let mut title = None;
     let mut slug = None;
+    let mut pov = None;
     let mut goal = None;
     let mut set = |meta: Meta, value: String| match meta {
         Meta::Title => title = Some(value),
         Meta::Slug => slug = Some(value),
+        Meta::Pov => pov = Some(value),
         Meta::WordCount => goal = parse_goal(&value),
     };
 
@@ -173,6 +179,7 @@ pub fn parse(markdown: &str, marker: &str) -> Header {
     Header {
         title: title.filter(|s| !s.is_empty()),
         slug: slug.filter(|s| !s.is_empty()),
+        pov: pov.filter(|s| !s.is_empty()),
         goal,
         body: body_lines.join("\n").trim().to_string(),
     }
@@ -265,4 +272,15 @@ mod tests {
         let md = "# Title: Plain\n### Rough Draft:\n\nText.";
         assert_eq!(parse(md, MARKER).goal, None);
     }
+
+    #[test]
+    fn parses_pov_at_heading_level_two() {
+        let md = "# Title: Bixby\n## POV: Bixby\n### Rough Draft:\n\nThe prose.";
+        let h = parse(md, MARKER);
+        assert_eq!(h.pov.as_deref(), Some("Bixby"));
+        assert_eq!(h.body, "The prose.");
+        // A prose line that merely starts with "POV" is not metadata.
+        let md2 = "### Rough Draft:\n\nPOV of the crowd was tense.";
+        assert_eq!(parse(md2, MARKER).pov, None);
+    }
 }