Allow disabling thinking via yaml with thinking_budget: 0 or none

[krissetto]

Configs like this will disable thinking. If re-enabled with /think, default budgets will be used based on the model provider

models:
  # Using string "none"
  gpt-no-thinking:
    provider: openai
    model: gpt-5
    thinking_budget: none # or 0

  # Using integer 0
  claude-no-thinking:
    provider: anthropic
    model: claude-sonnet-4-5
    thinking_budget: 0 # or none