Add environment lifecycle orchestration to McpEnv

[Timandes]

Summary

Extend rock.sdk.mcp.McpEnv to consume ScaffoldHub EnvLifecycleFactory and orchestrate environment lifecycles within the existing ROCK runtime flow.

Scope

• construct registered environment lifecycles by MCP server key
• inject the ROCK sandbox and start environment lifecycles before the user before_launch hook
• make McpEnv.is_alive(key: str | None = None) asynchronous and aggregate lifecycle status without short-circuiting
• release environment lifecycles before runtime/auth cleanup while preserving cleanup and error-priority semantics
• update the optional mcp dependency only after an actual ScaffoldHub release containing EnvLifecycle is available

Acceptance criteria

• unit tests cover construction, start order/config, async liveness, release order, cleanup continuation, and error propagation
• existing MCP integration tests collect with awaited is_alive calls
• relevant Ruff checks pass
• PR references this issue

Dependency

ScaffoldHub feature/env-lifecycle must provide EnvLifecycle, EnvLifecycleFactory, and GoogleSheetsEnvLifecycle under the fixed google_sheet server key.