docs(red-team): add MCP-based Quick Start and nest under Red Teaming

[Aryansharma28]

Summary

• New /advanced/red-teaming/quick-start page: 5-step MCP-driven flow (install scenario, configure LangWatch MCP, paste redteam my agents using langwatch, run tests, view in Simulations dashboard). Python and TypeScript code examples verified against the current public API.
• Sidebar: convert the flat Red Teaming entry under Advanced into a nested group with Quick Start first, Overview second.
• Overview (red-teaming.mdx): add a short "Why red teaming?" section near the top explaining the multi-turn rationale and linking to Quick Start. Removed the Roadmap section.

API verification

Python (python/scenario/__init__.py, red_team_agent.py):

• scenario.RedTeamAgent.crescendo(target, model, total_turns) ✓
• .marathon_script(checks, final_checks) — no turns param ✓
• configure, AgentAdapter, AgentInput, AgentReturnTypes, ScenarioState, JudgeAgent, run ✓

TypeScript (javascript/src/):

• scenario.redTeamCrescendo({ target, model, totalTurns }) ✓
• scenario.judgeAgent({ criteria }) (lowercase factory) ✓
• scenario.AgentRole.AGENT, ScenarioExecutionStateLike, state.lastAgentMessage() ✓
• .marathonScript({ checks, finalChecks }) ✓

Test plan

• pnpm --filter docs dev renders both pages without errors
• Sidebar shows Red Teaming → Quick Start, Overview under Advanced
• /advanced/red-teaming still resolves (deep links not broken)
• /advanced/red-teaming/quick-start renders with working code-groups and callouts
• Link from Overview's "Why red teaming?" section jumps to Quick Start

🤖 Generated with Claude Code

[github-actions]

Automated low-risk assessment

This PR was evaluated against the repository's Low-Risk Pull Requests procedure.

• Scope: Adds docs/pages/advanced/red-teaming/quick-start.mdx, updates docs/pages/advanced/red-teaming.mdx (adds a "Why red teaming?" section and removes the Roadmap), and adjusts docs navigation in docs/vocs.config.tsx to nest Red Teaming with Quick Start and Overview.
• Exclusions confirmed: no changes to auth, security settings, database schema, business-critical logic, or external integrations.
• Classification: low-risk-change under the documented policy.

The changes are limited to documentation and the docs site configuration: a new Quick Start MDX page, a small content edit to the Red Teaming overview, and a sidebar/navigation restructure. No authentication/authorization, secrets (only a placeholder API key in docs), encryption, database schemas, business‑critical logic, or runtime third‑party integrations are modified, so this meets the low‑risk criteria.

This classification allows merging without manual review once all required CI checks are passing and branch protection rules are satisfied.