v0.108.0 — HITL streaming everywhere

Completes the streaming item on fork issue #4: every provider Stream handler now resolves pending approvals at stream start and, on client-executed or approval-required tool calls, yields ToolApprovalRequestEvents and ends the stream with FinishReason::ToolCalls — DeepSeek, Gemini, Groq, Mistral, Ollama, OpenRouter, Qwen, Requesty, Vertex, xAI, Z, and OpenAI ChatCompletions join Anthropic + OpenAI Responses.

Suite: 1868 passing, PHPStan clean.