OpenCode Go: doc URL incorrect + MiniMax pricing discrepancies

Was checking the opencode-go provider data against the docs at https://opencode.ai/docs/go and found a few things off.

1. Provider doc link goes to the wrong page

providers/opencode-go/provider.toml has doc = "https://opencode.ai/docs/zen". The Go subscription has its own docs page now at https://opencode.ai/docs/go.

2. MiniMax M2.7 is missing cache_write pricing

The docs list cache_write at $0.375/M for M2.7 but the TOML only has cache_read = 0.06 and no cache_write field at all.

3. MiniMax M2.5 has wrong cache_read and missing cache_write

cache_read is set to 0.03 but the docs say $0.06/M. And cache_write = 0.375 is missing from the TOML. Looks like cache_read might have been halved by mistake.

The rest checks out. All 14 active model IDs match. The dual-package setup (provider default @ai-sdk/openai-compatible, per-model override to @ai-sdk/anthropic for MiniMax and Qwen models) lines up with the endpoint table. Pricing on everything else matches. The three deprecated models are marked correctly.

Open providers/opencode-go/provider.toml and compare its doc URL and MiniMax M2.5/M2.7 pricing fields with https://opencode.ai/docs/go. Update the incorrect link and cache pricing, then verify that the listed model IDs, package overrides, and remaining prices are unchanged and match the documentation.