New CLAUDE_CODE_SUBAGENT_EFFORT sets a default effort for subagents

Subagents are helper agents Claude starts to handle part of a task. Effort is how much reasoning the model puts into its work. Before, a subagent took the session's effort unless its own definition set one.

The new environment variable CLAUDE_CODE_SUBAGENT_EFFORT changes that:

• When an agent definition has no effort of its own, the level set in the variable is used.
• The value inherit is accepted.
• Any other value Claude Code does not recognise is recorded as an unknown level.

The documentation for Workflow scripts now says opts.effort defaults to the configured subagent default when this is set, instead of the session's effort. The variable can also be set through the environment section of Claude Code's settings, like CLAUDE_CODE_SUBAGENT_MODEL_FORCE.