fix: find-block off-by-one line_count for files with trailing newline (#91)

* fix: find-block off-by-one line_count for files with trailing newline

The find_block command was using `entries.len()` for line_count, but
`entries` comes from `normalized.split('\n')` which includes an empty
trailing entry when the file ends with a newline.

The fix uses `fc.len()` which correctly counts newlines (matching the
`read` command behavior).

Added regression tests for both cases:
- Files without trailing newline
- Files with trailing newline (the off-by-one scenario)

* fix: same off-by-one line_count in MCP handle_find_block

Author: quangdang46

crates/core/src/commands/find_block.rs

@@ -81,7 +81,7 @@ pub fn find_block_payload(
 
     Ok(FindBlockPayload {
         file: fc.path.display().to_string(),
-        line_count: entries.len(),
+        line_count: fc.len(),
         language,
         block_lines,
     })
@@ -634,4 +634,32 @@ mod tests {
         assert_eq!(payload.block_lines.len(), 3);
         assert!(payload.block_lines[0].content.contains("if true"));
     }
+
+    /// Regression: line_count must match fc.len(), not entries.len(), so files
+    /// with a trailing newline do not report an off-by-one count (Issue #90).
+    #[test]
+    fn test_line_count_no_trailing_newline() {
+        let content = "line1\nline2\nline3";
+        let (fc, entries) = make_fc(content, "test.txt");
+        let payload = find_block_payload(&fc, &entries, &anchor_for(1, &entries)).unwrap();
+        assert!(!fc.trailing_newline);
+        assert_eq!(fc.len(), 3);
+        // When there is no trailing newline, entries and fc.len() happen to
+        // agree, but we assert the semantic field regardless.
+        assert_eq!(payload.line_count, fc.len());
+        assert_eq!(payload.line_count, 3);
+    }
+
+    #[test]
+    fn test_line_count_with_trailing_newline() {
+        let content = "line1\nline2\nline3\n";
+        let (fc, entries) = make_fc(content, "test.txt");
+        let payload = find_block_payload(&fc, &entries, &anchor_for(1, &entries)).unwrap();
+        assert!(fc.trailing_newline);
+        assert_eq!(fc.len(), 3);
+        // entries.len() would be 4 here (includes the empty split tail).
+        // The fix ensures line_count comes from fc.len().
+        assert_eq!(payload.line_count, fc.len());
+        assert_eq!(payload.line_count, 3);
+    }
 }

crates/core/src/mcp.rs

@@ -263,7 +263,7 @@ fn handle_find_block(file: &str, anchor_str: &str) -> String {
     let mut out = format!(
         "File: {}  ({} lines)\nLanguage: {language}\n",
         fc.path.display(),
-        entries.len()
+        fc.len()
     );
     for i in start..=end {
         let entry = &entries[i];