Add flexible /roll command for custom dice rolls

[FirebrickRed]

Priority: MEDIUM
Status: TODO
Phase: Alpha-ready

Description

Add a flexible /roll command that allows players to roll any combination of dice with modifiers, separate from the skill-based rolling system in Issue #55.

Use Cases

• Rolling damage: /roll 2d6+3 (longsword + STR)
• Rolling hit dice: /roll 1d8 (wizard hit die)
• Rolling multiple dice: /roll 4d6 (ability score generation)
• Complex rolls: /roll 2d8+1d6+5 (smite damage)
• Advantage/disadvantage: /roll 2d20adv+5 or /roll 2d20dis+3

Proposed Syntax

/roll <dice_expression> [reason]

Examples:
/roll 1d20+5              → Roll 1d20, add 5
/roll 2d6+3               → Roll 2d6, add 3
/roll 1d4                 → Roll 1d4
/roll 2d20adv+7           → Roll 2d20 advantage, add 7
/roll 1d20+5 attack       → Roll with reason "attack"

Related Issues

• Issue Interactive Character Sheet: Skills Drilldown and Rolling System #55: Skill-based rolling (character sheet integration)

Future Enhancements

• Private rolls (DM only)
• Roll macros/saved expressions
• Critical hit/fail detection