Feat/vault encrypted storage

[linuxdevel]

This pull request adds comprehensive documentation for SafeClaw, including a high-level architecture overview and a step-by-step getting started guide. The new docs clarify system components, package boundaries, security model, onboarding flow, and extension points for developers.

Architecture and System Design

• Added docs/architecture.md detailing the overall system architecture, including a diagram of core components (channel adapters, gateway, session manager, agent, sandbox, vault, audit log, capability registry), their interactions, and the request/data flow.
• Documented package structure and dependency boundaries for the six SafeClaw packages, specifying the responsibilities and dependencies of each.

Developer Extension Points

• Explained how to implement new messaging surfaces via the ChannelAdapter interface and new tools via the ToolHandler interface, including code examples for both.
• Outlined the skill system workflow for third-party skill development, including manifest loading, signature verification, capability registration, and enforcement.

Getting Started and Onboarding

• Added docs/getting-started.md with prerequisites, installation instructions, kernel capability checks, and a detailed five-step onboarding wizard (kernel check, GitHub auth, vault creation, signing key generation, model selection).
• Provided usage instructions for CLI and WebChat adapters, security headers for webchat, audit command, and configuration overview.