Add HK as supported region.

[nodew]

Add HK as supported region.

Description

As title.

Motivation and Context

Support train model for HK stock market.

Types of changes

• Fix bugs
• Add new feature
• Update documentation

[nodew]

It seems that the pipeline is broken, the error isn't related to my changes.

[Abhijais4896]

REG_HK: {
"trade_unit": 100,
"limit_threshold": 0.1,
"deal_price": "close",

[Abhijais4896]

REG_HK: {
"trade_unit": 100,
"limit_threshold": 0.1,
"deal_price": "close",

[nodew]

@Abhijais4896 Sorry, I don't get your point, could you please add more description?

[Abhijais4896]

REG_CN = "cn"
REG_US = "us"
REG_TW = "tw"
REG_HK = "hk"

Epsilon for avoiding division by zero.

EPS = 1e-12

[Abhijais4896]

REG_HK: {
"trade_unit": 100,
"limit_threshold": 0.1,
"deal_price": "close",
},
}

[sunnynie2025]

Thanks for adding HK market support!

I have a few suggestions regarding the configuration values:

1. limit_threshold should be None

Hong Kong stocks do not have price limits (涨跌停). Unlike A-shares (9.5%) or Taiwan stocks (10%), HK stocks can move freely without
daily price limits.

# Current (incorrect)
"limit_threshold": 0.1,

# Suggested (correct)
"limit_threshold": None,

2. trade_unit consideration

HK stock lot sizes vary by stock (100, 500, 1000, 2000, etc.), not a fixed 100. Setting trade_unit: 1 might be more flexible, similar to  
the US market configuration.

# Current
"trade_unit": 100,

# Alternative (more flexible, like REG_US)
"trade_unit": 1,

Reference: https://www.hkex.com.hk/Services/Trading/Securities/Overview/Trading-Mechanism?sc_lang=en

---
For comparison, here's the current _default_region_config:
┌────────────────┬────────────┬─────────────────┐
│     Region     │ trade_unit │ limit_threshold │
├────────────────┼────────────┼─────────────────┤
│ CN             │ 100        │ 0.095           │
├────────────────┼────────────┼─────────────────┤
│ US             │ 1          │ None            │
├────────────────┼────────────┼─────────────────┤
│ TW             │ 1000       │ 0.1             │
├────────────────┼────────────┼─────────────────┤
│ HK (suggested) │ 1          │ None            │
└────────────────┴────────────┴─────────────────┘
---