Class table formatting support (`::: classtable` block syntax)

[Dev-Ray-Hunt]

Summary

Add support for rendering character class progression tables with D&D book styling using a dedicated callout syntax.

Desired Syntax

> [!classtable] The Ember Agent
> | Level | Prof. Bonus | Features | Ember Dice | Surge Limit |
> |-------|-------------|----------|------------|-------------|
> | 1st   | +2          | Ember Sense | 2d6     | 1           |
> | 2nd   | +2          | Field Training | 2d6  | 1           |

Visual Requirements

• Full column width
• Colored/styled header row (D&D orange/gold)
• Compact row height
• Small-caps column headers
• Alternating row shading
• Title row spanning all columns

Notes

This extends the existing Obsidian callout transformer in renderer.ts. The rpg-callout-classtable class needs corresponding CSS in default-theme.css.