claude.ai MCP integrations not available in sessions launched from the agents view

When launching background agent sessions from the agents view (claude agents), claude.ai-managed MCP integrations (Slack, Amplitude, Asana, etc.) are not injected into those sessions, even though the parent session has them available and the user is actively authenticated.

Current behavior: Background agent sessions launched from the agents view authenticate via API key, so they don't receive the claude.ai account's MCP servers.

Expected behavior: Since the agents view is an interactive, user-present context and the user is already authenticated with their claude.ai account, child sessions should inherit (or be granted access to) the same claude.ai-managed MCP servers as the parent session.

Why this matters: The agents view is designed for humans running multiple parallel sessions. Those sessions need access to the same integrations (e.g. post to Slack, query Amplitude) that interactive sessions have. The OAuth/auth concern that applies to truly headless/unattended sessions doesn't apply here -- a human launched the session and is actively monitoring it.

Suggested fix: When a background session is spawned from an authenticated claude.ai parent session in the agents view, pass down the account's MCP server context to the child process.