Rust grid crate CVE-2026-42199

The grid crate (CPE: cpe:2.3:a:becheran:grid:*:*:*:*:*:*:*:*) is a Rust library providing a two-dimensional data structure backed by a contiguous Vec<T>. The root cause is CWE-190 (Integer Overflow or Wraparound): expand_rows() computed new backing-vector lengths using unchecked arithmetic (self.data.len() + rows * self.cols), which silently wraps in Rust release builds when the multiplication or subsequent addition overflows usize. The resulting undersized allocation breaks the invariant that logical grid dimensions must match physical backing storage. For ColumnMajor grids, index computations derived from the now-incorrect total_rows produce invalid slice ranges before metadata is even updated. Finally, self.rows += rows stores the logically correct but physically unsupported row count, causing the safe get() method to invoke the unsafe get_unchecked() with an out-of-bounds index - violating Rust's memory safety guarantees even in entirely #[forbid(unsafe_code)] consumer code. The fix in v1.0.1 replaces all four affected arithmetic sites (expand_rows, expand_cols, prepend_rows, prepend_cols) with checked_add/checked_mul helpers that panic on overflow, preserving grid integrity.