Replace all `declare -A` (associative arrays, Bash 4+ only) with simple
variables and helper functions. Fixes crash on macOS default Bash 3.2:
- "operand expected" at line 40
- "meta: unbound variable" at line 43
Reported by community user (Slack).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>