Function getTamilYoga

getTamilYoga(
weekday: number,
nakIdx: number,
): { name: string; type: "auspicious" | "inauspicious" | "neutral" }
Get the Tamil Yoga classification (Amrita etc.).

A regional interpretive layer used in tandem with the Anandadi sequence.
Parameters
- weekday: number
  0=Sun, ..., 6=Sat
- nakIdx: number
  0-based index in the 28-system
Returns { name: string; type: "auspicious" | "inauspicious" | "neutral" }
Classification mapping (Amrita/Siddha/Marana)