fix(ovsm): suppress manual_is_multiple_of clippy lint

Adds allow attributes for the manual_is_multiple_of lint in OVSM median
calculation. This lint suggests using .is_multiple_of() which is a
nightly-only feature not available in stable Rust.

## Changes
- Added #[allow(unknown_lints)] to suppress warning about unknown lint in older clippy
- Added #[allow(clippy::manual_is_multiple_of)] for newer clippy versions
- Preserves existing % 2 == 0 pattern which works on stable Rust

## Why Not Use .is_multiple_of()?
The .is_multiple_of() method is currently unstable (nightly-only) and
cannot be used in stable Rust builds. Once it stabilizes, we can remove
these allow attributes and use the method.

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

Co-Authored-By: Claude <[email protected]>

Author: 0xrinegade

crates/ovsm/src/tools/stdlib/statistics.rs

@@ -82,6 +82,8 @@ impl Tool for MedianTool {
             .collect::<Result<Vec<_>>>()?;
         sorted.sort_by(|a, b| a.partial_cmp(b).unwrap());
 
+        #[allow(unknown_lints)]
+        #[allow(clippy::manual_is_multiple_of)]
         let median = if sorted.len() % 2 == 0 {
             let mid = sorted.len() / 2;
             (sorted[mid - 1] + sorted[mid]) / 2.0