fix(search): collapse newlines in snippets to prevent unindented metadata (GIT-5)

Document content_text includes multi-line metadata (Project:, URL:, Labels:,
State:) separated by newlines. FTS5 snippet() preserves these newlines, causing
subsequent lines to render at column 0 with no indent. collapse_newlines()
flattens all whitespace runs into single spaces before truncation and rendering.

Includes 3 unit tests.

src/cli/commands/search.rs

@@ -337,6 +337,27 @@ fn parse_json_array(json: &str) -> Vec<String> {
         .collect()
 }
 
+/// Collapse newlines and runs of whitespace in a snippet into single spaces.
+///
+/// Document `content_text` includes multi-line metadata (Project:, URL:, Labels:, etc.).
+/// FTS5 snippet() preserves these newlines, causing unindented lines when rendered.
+fn collapse_newlines(s: &str) -> String {
+    let mut result = String::with_capacity(s.len());
+    let mut prev_was_space = false;
+    for c in s.chars() {
+        if c.is_ascii_whitespace() {
+            if !prev_was_space {
+                result.push(' ');
+                prev_was_space = true;
+            }
+        } else {
+            result.push(c);
+            prev_was_space = false;
+        }
+    }
+    result
+}
+
 /// Truncate a snippet to `max_visible` visible characters, respecting `<mark>` tag boundaries.
 ///
 /// Counts only visible text (not tags) toward the limit, and ensures we never cut
@@ -499,12 +520,15 @@ pub fn print_search_results(response: &SearchResponse, explain: bool) {
         println!("{indent}{}", meta_parts.join(&sep));
 
         // Phase 5: limit snippet to ~2 terminal lines.
+        // First collapse newlines — content_text includes multi-line metadata
+        // (Project:, URL:, Labels:, etc.) that would print at column 0.
+        let collapsed = collapse_newlines(&result.snippet);
         // Truncate based on visible text length (excluding <mark></mark> tags)
         // to avoid cutting inside a highlight tag pair.
         let max_snippet_width =
             render::terminal_width().saturating_sub(render::visible_width(&indent));
         let max_snippet_chars = max_snippet_width.saturating_mul(2);
-        let snippet = truncate_snippet(&result.snippet, max_snippet_chars);
+        let snippet = truncate_snippet(&collapsed, max_snippet_chars);
         let rendered = render_snippet(&snippet);
         println!("{indent}{rendered}");
 
@@ -619,10 +643,7 @@ mod tests {
         // Should not cut inside a <mark> pair
         let open_count = result.matches("<mark>").count();
         let close_count = result.matches("</mark>").count();
-        assert_eq!(
+        assert_eq!(open_count, close_count, "unbalanced tags in: {result}");
-            open_count, close_count,
-            "unbalanced tags in: {result}"
-        );
     }
 
     #[test]
@@ -652,4 +673,32 @@ mod tests {
         // Very small limit should return as-is (guard clause)
         assert_eq!(truncate_snippet(s, 3), s);
     }
+
+    #[test]
+    fn collapse_newlines_flattens_multiline_metadata() {
+        let s = "[[Issue]] #4018: Remove math.js\nProject: vs/typescript-code\nURL: https://example.com\nLabels: []";
+        let result = collapse_newlines(s);
+        assert!(
+            !result.contains('\n'),
+            "should not contain newlines: {result}"
+        );
+        assert_eq!(
+            result,
+            "[[Issue]] #4018: Remove math.js Project: vs/typescript-code URL: https://example.com Labels: []"
+        );
+    }
+
+    #[test]
+    fn collapse_newlines_preserves_mark_tags() {
+        let s = "first line\n<mark>keyword</mark>\nsecond line";
+        let result = collapse_newlines(s);
+        assert_eq!(result, "first line <mark>keyword</mark> second line");
+    }
+
+    #[test]
+    fn collapse_newlines_collapses_runs_of_whitespace() {
+        let s = "a  \n\n  b\t\tc";
+        let result = collapse_newlines(s);
+        assert_eq!(result, "a b c");
+    }
 }