Claude Code v2.1.23 → v2.1.25: Gateway beta validation fix

[claude-yolo]

WHY this matters: Enterprise users on Bedrock/Vertex were hitting 400 errors when beta features disabled

Key fix: Fixed beta header validation error for gateway deployments
Setting: CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1 now works properly

Also includes: expanded analytics docs, API doc refreshes, new Agent SDK streaming docs

Link: #631