Anthropic adaptive thinking

[GrahamCampbell]

Description

Add support for Anthropic's adaptive thinking mode (thinking.type: "adaptive") and the effort parameter (output_config.effort), recommended for Claude 4.6+ models. The legacy thinking.enabled + budgetTokens configuration remains fully supported for older models.

New provider options:

->withProviderOptions([
    'thinking' => ['type' => 'adaptive'],
    'effort' => 'high', // low, medium, high (default), max (Opus 4.6 only)
])

Changes:

• Text.php / Structured.php: Extract resolveThinking() helper to support both adaptive and legacy thinking payloads; add output_config.effort to the request payload
• NativeOutputFormatStructuredStrategy.php: Merge output_config instead of overwriting, so effort and format coexist
• ExtractsThinking.php: Extract thinking blocks from responses when adaptive thinking is active
• ToolStructuredStrategy.php: Skip tool_choice for adaptive thinking (Anthropic restriction)
• Tests restructured with adaptive thinking as the primary configuration and legacy as secondary
• Documentation updated to recommend adaptive thinking for Claude 4.6+ models

Breaking Changes

None. The existing thinking.enabled + budgetTokens API is unchanged and continues to work.