Add Claude Code toolchain detection, version checks, auth checks, and update actions

[KSemenenko]

Problem

dotPilot must expose whether Claude Code is installed, authenticated, current, and ready for session use.

Scope

• Detect the local Claude Code executable, version, auth state, and update availability
• Define operator actions for install, reconnect, troubleshoot, and update
• Make provider readiness visible before session creation

Out of scope

• Claude session execution and streaming behavior
• Shared Toolchain Center shell behavior that belongs in the UI issue

Implementation notes

• Use ManagedCode.ClaudeCodeSharpSDK metadata and update capabilities where appropriate
• Keep the issue focused on readiness and actions
• Ensure MCP-related prerequisite visibility is compatible with later provider work

Definition of Done

• The issue defines the Claude Code readiness contract and operator actions
• The issue is specific enough to implement without inventing hidden assumptions later

Verification

• Review the issue against Toolchain Center UI and provider adapter plans

Dependencies

• Parent epic: [Epic] Build the provider toolchain center for Codex, Claude Code, and GitHub Copilot #14