feat: add CLI passthrough flags for Claude session options

[sonwr]

Summary

• add first-class CLI flags for --model, --allowed-tools, and --max-turns
• validate and plumb the flags through runOnce/createSession/ensureSession
• send Claude-specific session options through ACP session/new _meta.claudeCode.options
• add unit and integration coverage for parsing, help output, and ACP metadata forwarding

Testing

• pnpm run build:test
• node --test dist-test/test/client.test.js dist-test/test/cli.test.js dist-test/test/integration.test.js

Closes #49

[frankekn]

Superseded by #94, which carries the same Claude session-option passthrough feature on top of current main and runs CI in the main repository.

Thanks for the original implementation here.