fix: 移除 Antigravity 模式下 Claude 4.6 的遗留硬编码映射

[sz30]

Fixes #421

问题说明

Antigravity 现在会直接返回真实可用的 Claude 模型 ID，例如：

• claude-opus-5-5-low
• claude-opus-5-5-medium
• claude-opus-5-5-high
• claude-sonnet-5-5-low
• claude-sonnet-5-5-medium
• claude-sonnet-5-5-high

但 gcli2api 在请求规范化阶段仍会根据 opus / sonnet 关键词，
将 Claude 模型强制映射到硬编码的 4.6 模型 ID。

由于 Claude 4.6 已被 Antigravity 下线，这会导致新模型请求被错误改写。

修改内容

移除了过时的 Claude 模型名称 remapping。
经实测 Antigravity 现在已经返回真实模型 ID，因此这里可以直接保留原始 model ID，
无需再根据 opus / sonnet 等关键词把 Claude 模型强制映射到某个固定版本。

测试结果

已实际测试以下全部 6 个模型，均可正常调用：

• claude-sonnet-5-5-low
• claude-sonnet-5-5-medium
• claude-sonnet-5-5-high
• claude-opus-5-5-low
• claude-opus-5-5-medium
• claude-opus-5-5-high

测试log

root@xx:/home/gcli2api# curl -s
-X POST
http://127.0.0.1:7861/antigravity/v1/chat/completions
-H "Content-Type: application/json"
-H "Authorization: Bearer xx"
-d '{
"model": "claude-sonnet-5-5-medium",
"messages": [
{
"role": "user",
"content": "Reply with OK"
}
],
"stream": false
}'
{"id":"5f299fbd-a8ee-4116-ab53-531ee5c48a97","object":"chat.completion","created":1791xxx755,"model":"claude-sonnet-5-5-medium","choices":[{"index":0,"message":{"role":"assistant",root@xx:/home/gcli2api# curl -s \stop"}],"usage":{"prompt_tokens":14,"completion_tokens":4,"total_tokens":18}}

root@xx:/home/gcli2api# curl -s
-X POST
http://127.0.0.1:7861/antigravity/v1/chat/completions
-H "Content-Type: application/json"
-H "Authorization: Bearer xx"
-d '{
"model": "claude-opus-5-5-low",
"messages": [
{
"role": "user",
"content": "Reply with OK"
}
],
"stream": false
}'
{"id":"fa289fc9-4b20-4d50-8a65-985e92deda39","object":"chat.completion","created":1791xxx832,"model":"claude-opus-5-5-low","choices":[{"index":0,"message":{"role":"assistant","controot@xx:/home/gcli2api# curl -s }],"usage":{"prompt_tokens":14,"completion_tokens":4,"total_tokens":18}}

root@xx:/home/gcli2api# curl -s
-X POST
http://127.0.0.1:7861/antigravity/v1/chat/completions
-H "Content-Type: application/json"
-H "Authorization: Bearer xx"
-d '{
"model": "claude-sonnet-5-5-high",
"messages": [
{
"role": "user",
"content": "Reply with OK"
}
],
"stream": false
}'
{"id":"3e4e0a82-bcb2-4999-a246-18dbb391a2e2","object":"chat.completion","created":1791xxx862,"model":"claude-sonnet-5-5-high","choices":[{"index":0,"message":{"role":"assistant","croot@xx:/home/gcli2api# curl -s \op"}],"usage":{"prompt_tokens":14,"completion_tokens":4,"total_tokens":18}}

root@xx:/home/gcli2api# curl -s
-X POST
http://127.0.0.1:7861/antigravity/v1/chat/completions
-H "Content-Type: application/json"
-H "Authorization: Bearer xx"
-d '{
"model": "claude-sonnet-5-5-medium",
"messages": [
{
"role": "user",
"content": "Reply with OK"
}
],
"stream": false
}'
{"id":"59c8bdb4-5acf-4460-92d0-11dec8def7dd","object":"chat.completion","created":1791xxx881,"model":"claude-sonnet-5-5-medium","choices":[{"index":0,"message":{"role":"assistant",root@xx:/home/gcli2api# curl -s \stop"}],"usage":{"prompt_tokens":14,"completion_tokens":4,"total_tokens":18}}

root@xx:/home/gcli2api# curl -s
-X POST
http://127.0.0.1:7861/antigravity/v1/chat/completions
-H "Content-Type: application/json"
-H "Authorization: Bearer xx"
-d '{
"model": "claude-opus-5-5-high",
"messages": [
{
"role": "user",
"content": "Reply with OK"
}
],
"stream": false
}'
{"id":"5e701a1d-d08e-4a7a-8d0b-5ed372b7544b","object":"chat.completion","created":1791xxx900,"model":"claude-opus-5-5-high","choices":[{"index":0,"message":{"role":"assistant","conroot@xx:/home/gcli2api# curl -s "}],"usage":{"prompt_tokens":14,"completion_tokens":4,"total_tokens":18}}

root@xx:/home/gcli2api# curl -s
-X POST
http://127.0.0.1:7861/antigravity/v1/chat/completions
-H "Content-Type: application/json"
-H "Authorization: Bearer xx"
-d '{
"model": "claude-sonnet-5-5-low",
"messages": [
{
"role": "user",
"content": "Reply with OK"
}
],
"stream": false
}'
{"id":"0d8cd0ef-5934-4c54-89b4-6d7c578e8267","object":"chat.completion","created":1791xxx918,"model":"claude-sonnet-5-5-low","choices":[{"index":0,"message":{"role":"assistant","content":"OK"},"finish_reason":"stop"}],"usage":{"prompt_tokens":14,"completion_tokens":4,"total_tokens":18}}