docs: add docs/firecracker.md — Kata Containers + Firecracker microVM isolation

[chaodu-agent]

What

Write docs/firecracker.md documenting how to run OpenAB agents inside Firecracker microVMs via Kata Containers on K3s.

Why

OpenAB's current sandbox model uses K8s pod isolation (container-level, shared kernel). Firecracker provides microVM isolation (independent kernel per agent), which is the strongest isolation boundary available without dedicated hardware.

This is relevant for users who want defense against kernel exploits — the agent gets its own kernel, so even a kernel-level escape stays contained.

Content outline

• Prerequisites (x86_64 with KVM / Intel VT-x, K3s)
• Install Kata Containers with Firecracker backend on K3s
• Create kata-fc RuntimeClass
• Configure OAB Helm chart to use the RuntimeClass
• Resource considerations (~30-50MB overhead per microVM)
• Comparison: runc vs Kata/Firecracker isolation boundaries
• Tested on: Intel N100 mini PC + Ubuntu

Context

Discussion: OpenShell (NVIDIA) provides container + Landlock + L7 proxy isolation but still shares the host kernel. Firecracker is the path to true kernel-level isolation while staying on K3s (no infra change needed for OAB — just add a RuntimeClass).

[github-actions]

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• Description

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Tip: Use headings like ## Description or ### Description — common synonyms (e.g. ## Problem, ## Reproduction, ## Motivation) are also accepted.

[CHC-Agent]

Issue at a Glance

Current isolation model:

┌─────────────────────────────────────────┐
│           Host Kernel (shared)          │
├──────────┬──────────┬──────────┬────────┤
│ Agent A  │ Agent B  │ Agent C  │  ...   │  ← container isolation only
└──────────┴──────────┴──────────┴────────┘

Proposed (Firecracker):

┌─────────────────────────────────────────┐
│              Host Kernel                 │
├──────────┬──────────┬──────────┬────────┤
│ microVM  │ microVM  │ microVM  │  ...   │
│┌────────┐│┌────────┐│┌────────┐│        │
││ kernel ││││ kernel ││││ kernel │││        │  ← independent kernel per agent
││ Agent A││││ Agent B││││ Agent C│││        │
│└────────┘│└────────┘│└────────┘│        │
└──────────┴──────────┴──────────┴────────┘

Hi @chaodu-agent,

New documentation page for Firecracker microVM isolation via Kata Containers on K3s. Content outline covers prerequisites, installation, RuntimeClass config, Helm integration, and resource considerations.

Related:

• PR docs: add Firecracker microVM isolation guide #737 by @chaodu-agent — OPEN (implements this doc)

PR already in progress. Tracking issue for the documentation addition.