chore: upgrade Rust toolchain to 1.95.0 (#3390)

Bumps the pinned toolchain in `rust-toolchain.toml` from 1.94.0 to
1.95.0.

Fixes new lints surfaced by clippy on 1.95.0:

- `manual_checked_ops` — fragment size mean in `table.rs` uses
`checked_div`
- `explicit_counter_loop` — shuffle test loop in `shuffle.rs`

No rustc warnings were introduced.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

rust-toolchain.toml

@@ -1,2 +1,2 @@
 [toolchain]
-channel = "1.94.0"
+channel = "1.95.0"

rust/lancedb/src/dataloader/permutation/shuffle.rs

@@ -464,11 +464,9 @@ mod tests {
         let mut iter = ids.into_iter().map(|o| o.unwrap());
         while let Some(first) = iter.next() {
             let rows_left_in_clump = if first == 4470 { 19 } else { 29 };
-            let mut expected_next = first + 1;
-            for _ in 0..rows_left_in_clump {
+            for expected_next in (first + 1)..=(first + rows_left_in_clump) {
                 let next = iter.next().unwrap();
                 assert_eq!(next, expected_next);
-                expected_next += 1;
             }
         }
     }

rust/lancedb/src/table.rs

@@ -3015,11 +3015,12 @@ impl BaseTable for NativeTable {
         let p99 = *sorted_sizes.get(num_fragments * 99 / 100).unwrap_or(&0);
         let min = sorted_sizes.first().copied().unwrap_or(0);
         let max = sorted_sizes.last().copied().unwrap_or(0);
-        let mean = if num_fragments == 0 {
-            0
-        } else {
-            sorted_sizes.iter().copied().sum::<usize>() / num_fragments
-        };
+        let mean = sorted_sizes
+            .iter()
+            .copied()
+            .sum::<usize>()
+            .checked_div(num_fragments)
+            .unwrap_or(0);
 
         let frag_stats = FragmentStatistics {
             num_fragments,