feat: add multi-agent security control plane

[madhyamakist]

Summary

• Adds a cached multi-agent control plane for completed security runs: Supervisor, Threat Analyst, Red Team, Remediation Engineer, Compliance Mapper, Evidence QA, and Reporter.
• Adds /api/agents/catalog and /api/runs/{run_id}/agent-mesh, and includes the mesh in evidence bundles.
• Adds an Agent mesh UI tab plus report-panel summary and updates Vanguard by Zer0 visible product naming.
• Documents the agent mesh and cost guardrail: provider calls are bounded with deterministic fallback, not loop-until-credits exhaustion.

Verification

• make test: 26 passed, frontend Vite build passed
• Live smoke on http://127.0.0.1:8011: /health OK; free scan run #21 completed; /api/runs/21/agent-mesh returned 7 agents; report returned completed with 6 findings
• Browser smoke: http://127.0.0.1:8011 rendered; Agent mesh tab showed 7 agents; console had 0 JS errors