[inureyes]

fix(rocm): clamp the remaining element-count HIP launch grids

The remaining HIP launchers that size a grid from the element or group count computed an uncapped int block count and ran one index per thread. HIP refuses a launch of 2^32 threads or more with hipErrorInvalidConfiguration, grid dimensions y and z top out at 65535 blocks, and int num_blocks overflows earlier, so every op that large failed; the elementwise row grid and the transpose tile grid failed outright past 65535 blocks of grid y.

Each launcher now computes its block count with rocm::copy_grid_blocks (64-bit, clamped to [1, 65535], the item 42 helpers in copy/copy.hpp) and each kernel walks its elements with a grid-stride loop over an int64_t counter. unary_g and ternary_g stride their rows on a 64-bit counter past the y cap and copy_col_row caps its 2-D tile grid at the launch limit with 64-bit tile indices. col_reduce_small also advanced its function-parameter pointers inside the loop, so past the cap the advances compounded and the kernel read and wrote out of bounds; they are now per-iteration locals. The change also repairs a stray extra closing brace in indexing.hip that split the namespaces and failed the build.

Reproduction: tests/rocm_hip_grid_clamp.rs runs each launcher family at a size past the 65535-block cap and compares every element with a host reference, 13 tests in total: 9 fast (68.8M elementwise elements at 67200 y-blocks, 21.3M gather and 16.8M scatter elements, 67.1M column-reduce outputs, 2^24 + 1 arange, argsort and transpose-copy elements) plus 4 #[ignore]d tests past 2^32 elements (8 GiB f16 elementwise, about 10.9 GiB gather) that failed in try_eval with hipErrorInvalidConfiguration before the fix. On this branch all 9 fast tests pass in 1.9 s; without the overlay changes the row-grid, tile-grid and col-reduce tests fail outright and the 2^32 tests abort the launch. LOCAL_FIXES.md item 46 records the change.

Closes #2234