[claude-code] Add CLI binary detection and auth status check (extension host) #761

Parent issue

#756

Depends on

#757

Context

The UI needs to know whether the claude CLI is installed and authenticated before showing a connected state. This adds a lightweight extension-host integration — no OAuth flow needed, just CLI availability detection.

Files

• src/integrations/claude-code/ (new directory)
• src/integrations/claude-code/cli.ts (new)
• Message handler registration in the extension host
• src/integrations/claude-code/__tests__/cli.spec.ts (new)

Work

• resolveClaudeBinaryPath(cliPath?: string): Promise<string>
  • Try cliPath first (support ~/ expansion via os.homedir())
  • Fall back to which claude (or where claude on Windows)
  • Throw with a helpful message if not found: "Claude CLI not found. Install it and run \claude login`."`
• Extension host message handler:
  • requestClaudeCodeAuthStatus → spawn claude --version, check exit code → reply { type: "claudeCodeAuthStatus", available: boolean, version?: string }

Tests

Mock child_process.exec:

• Custom cliPath is tried first
• ~/ in cliPath is expanded to os.homedir()
• Falls back to which claude when no custom path given
• Throws descriptive error when CLI not found
• Reply has available: false on non-zero exit
• Reply has available: true and parsed version on success

Acceptance criteria

• Binary path resolution works on macOS, Linux, and Windows
• Webview receives claudeCodeAuthStatus in response to requestClaudeCodeAuthStatus
• All tests pass