feat(minimax-coding-plan): add MiniMax-M3 token plan models

[coygeek]

Summary

Adds MiniMax-M3 to the MiniMax token-plan providers:

• providers/minimax-coding-plan/models/MiniMax-M3.toml
• providers/minimax-cn-coding-plan/models/MiniMax-M3.toml

This keeps the token-plan provider catalogs in parity with the M3 model metadata already present for OpenCode-specific MiniMax M3 routes, while preserving token-plan zero-cost catalog entries.

Why

MiniMax M3 is available to token-plan users, but minimax-coding-plan currently only lists M2.x models. Downstream tools that read Models.dev, including OpenCode, therefore cannot select minimax-coding-plan/MiniMax-M3 without a local registry override.

Local OpenCode smoke with an ephemeral Models.dev override containing this entry:

OPENCODE_MODELS_PATH=/tmp/opencode-models-minimax-m3.json \
  opencode run -m minimax-coding-plan/MiniMax-M3 \
  "Reply with exactly: MINIMAX_CODING_PLAN_M3_DIRECT_SMOKE_OK"

Output:

> build · MiniMax-M3
MINIMAX_CODING_PLAN_M3_DIRECT_SMOKE_OK

Verification

bun validate
bun ./packages/core/script/validate.ts > /tmp/models-dev-minimax-m3-final-validate.json
jq -r '.["minimax-coding-plan"].models["MiniMax-M3"].id, .["minimax-cn-coding-plan"].models["MiniMax-M3"].id' /tmp/models-dev-minimax-m3-final-validate.json
git diff --check

The generated catalog includes MiniMax-M3 for both token-plan providers.

[vinayakkulkarni]

Need this! Can we merge this?

[rekram1-node]

Closing in favor of: #1940