Expand test coverage from 23 pure helper tests to 53 tests covering
the full plugin: _cleanup, _remind_once, _remind_repeat, and the
complete cmd_remind handler (usage, oneshot, repeating, list, cancel,
target routing). Fix IndexError on `!remind every` with no arguments.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Supports duration parsing (5m, 1h30m, 2d12h), short hex IDs for
tracking, list/cancel subcommands, and repeating intervals via
`!remind every <duration> <text>`. Includes 23 unit tests.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
