fix: replace inline command definitions with static data table

Refactor get_all_commands() from ~150 inline Command struct literals
(each with 2 t!() macro expansions and nested vec![] calls) into a
static COMMAND_DEFS array with a small .map() loop. Reduces ~300 t!()
macro expansions to 2 and eliminates ~300 nested vec![] allocations,
significantly reducing LLVM IR size and compile time for this file.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sinelaw