feat(thinking): add adaptive thinking support for Claude models

Add support for Claude's "adaptive" and "auto" thinking modes using `output_config.effort`. Introduce support for new effort level "max" in adaptive thinking. Update thinking logic, validate model capabilities, and extend converters and handling to ensure compatibility with adaptive modes. Adjust static model data with supported levels and refine handling across translators and executors.

internal/thinking/convert.go

@@ -16,6 +16,9 @@ var levelToBudgetMap = map[string]int{
 	"medium":  8192,
 	"high":    24576,
 	"xhigh":   32768,
+	// "max" is used by Claude adaptive thinking effort. We map it to a large budget
+	// and rely on per-model clamping when converting to budget-only providers.
+	"max": 128000,
 }
 
 // ConvertLevelToBudget converts a thinking level to a budget value.
@@ -31,6 +34,7 @@ var levelToBudgetMap = map[string]int{
 //   - medium  → 8192
 //   - high    → 24576
 //   - xhigh   → 32768
+//   - max     → 128000
 //
 // Returns:
 //   - budget: The converted budget value