Feat/output token max env

[junmediatek]

Currently, the default max output token for opencode is 32,000, however, the latest models such as GPT, Gemini, and Claude now support max output tokens exceeding 64,000, so the current setting of 32,000 is no longer suitable.

Therefore, it is necessary to add a method to modify the max output token.

[junmediatek]

@rekram1-node could you help to check this PR?

[rekram1-node]

lgtm