OUTPUT_TOKEN_MAX hardcoded to 32k prevents using full 64k output limit for Claude Sonnet 4.5 with extended thinking

[calvinalkan]

Problem

Claude Sonnet 4.5 supports 64k output tokens, but OpenCode has a hardcoded limit
that prevents using the full capacity when extended thinking is enabled.

Current Behavior

In src/session/prompt.ts:

export const OUTPUT_TOKEN_MAX = 32_000

const outputLimit = Math.min(model.info.limit.output, OUTPUT_TOKEN_MAX) ||
OUTPUT_TOKEN_MAX

This caps outputLimit at 32k even when the model config specifies 64k:

"claude-sonnet-4-20250514": {
  "limit": {
    "output": 64000,
    "context": 200000
  }
}

When using extended thinking with a 32k budget:

thinking:
  type: enabled
  budgetTokens: 32000

The calculation becomes: 32000 - 32000 = 0, causing:

AI_InvalidArgumentError: maxOutputTokens must be >= 1

Expected Behavior

OUTPUT_TOKEN_MAX should be at least 64k to support Claude Sonnet 4.5's full output
capacity with extended thinking enabled.

Workaround

Reduce thinking budgets to fit within 32k total (e.g., budgetTokens: 20000 leaves
12k for output).

[rekram1-node]

hm we will need to adjust out logic for the budget tokens calculation...

[rekram1-node]

should be fixed in next release