feat: add Kiro provider with 11 models

[NachoFLizaur]

What does this PR do?

Adds Kiro (AWS CodeWhisperer) as a new provider with 11 models fetched from the ListAvailableModels API.

Models:

• auto (task-optimized routing, 1M context)
• claude-opus-4.6, claude-sonnet-4.6 (1M context)
• claude-opus-4.5, claude-sonnet-4.5, claude-sonnet-4, claude-haiku-4.5 (200K context)
• deepseek-3.2 (164K), minimax-m2.1 (196K), minimax-m2.5 (196K), qwen3-coder-next (256K)

Cost is 0 for all models (subscription-based, same as GitHub Copilot). Reasoning enabled on Claude models (thinking tool support in the opencode provider), disabled on non-Claude models (deepseek, minimax, qwen).

Schema updated to allow kiro as a custom npm provider without an api field.

Companion PR in opencode: Link

How did you verify?

• Model IDs, context limits, and output limits verified against the live ListAvailableModels API response
• Running Opencode with the updated model list after a Models.dev built using OPENCODE_MODELS_PATH showed the correct models and worked when interacting with them.