style: Apply cargo fmt and clippy fixes across codebase

Automated formatting and lint corrections from parallel agent work:

- cargo fmt: import reordering (alphabetical), line wrapping to respect
  max width, trailing comma normalization, destructuring alignment,
  function signature reformatting, match arm formatting
- clippy (pedantic): Range::contains() instead of manual comparisons,
  i64::from() instead of `as i64` casts, .clamp() instead of
  .max().min() chains, let-chain refactors (if-let with &&),
  #[allow(clippy::too_many_arguments)] and
  #[allow(clippy::field_reassign_with_default)] where warranted
- Removed trailing blank lines and extra whitespace

No behavioral changes. All existing tests pass unmodified.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/documents/truncation.rs

@@ -231,10 +231,7 @@ mod tests {
     #[test]
     fn test_first_last_oversized() {
         let big_body = "x".repeat(20_000);
-        let notes = vec![
-            make_note("alice", &big_body),
-            make_note("bob", &big_body),
-        ];
+        let notes = vec![make_note("alice", &big_body), make_note("bob", &big_body)];
         let result = truncate_discussion(&notes, 10_000);
         assert!(result.is_truncated);
         assert_eq!(result.reason, Some(TruncationReason::FirstLastOversized));
@@ -304,7 +301,11 @@ mod tests {
             .collect();
         let result = truncate_discussion(&notes, 12_000);
         assert!(result.is_truncated);
-        assert!(result.content.contains("[... 5 notes omitted for length ...]"));
+        assert!(
+            result
+                .content
+                .contains("[... 5 notes omitted for length ...]")
+        );
     }
 
     #[test]