Add Support for Targon API Provider

[philbb]

Targon is a fast and cost-efficient API Provider that offers several of the leading open source coding models.

It currently offers the following models at leading throughputs and prices:

• Kimi-K2-Instruct
• Qwen3-Coder-480B-A35B-Instruct
• Qwen3-235B-A22B-Instruct-2507
• DeepSeek-V3-0324
• DeepSeek-V3
• DeepSeek-R1
• DeepSeek-R1-0528

Access to the API is via either of the following 2 endpoints.
It would be great if Roo would support it natively.

curl https://api.targon.com/v1/chat/completions
-H "Content-Type: application/json"
-H "Authorization: Bearer YOUR_API_KEY"
-N
-d '{
"model": "moonshotai/Kimi-K2-Instruct",
"stream": true,
"messages": [
{"role": "system", "content": "You are a helpful programming assistant."},
{"role": "user", "content": "Write a bubble sort implementation in Python with comments explaining how it works"}
],
"temperature": 0.7,
"max_tokens": 100,
"top_p": 1,
"frequency_penalty": 0,
"presence_penalty": 0
}'

OR

curl https://api.targon.com/v1/completions
-H "Content-Type: application/json"
-H "Authorization: Bearer YOUR_API_KEY"
-N
-d '{
"model": "moonshotai/Kimi-K2-Instruct",
"stream": true,
"prompt": "The x y problem is",
"temperature": 0.7,
"max_tokens": 100,
"top_p": 1,
"frequency_penalty": 0,
"presence_penalty": 0
}'