Add README “Co dalej?” onboarding section

[Copilot]

The README needed a standing “Co dalej?” section that captures current project state and next steps for someone taking over the project without prior context.

• Onboarding state

  • Replaced the generic “Next step” section with Co dalej?.
  • Summarizes that the repo is still in Sprint 0 with no package.json, src/, or runnable game yet.

• Continuation guidance

  • Lists the first documents to read: brief, fabula, GDD, and architecture.
  • Preserves the intended Copilot workflow and prompt order.
  • Calls out that mechanics such as combat, traits, morale, progression, factions, and quest chains should not be invented before mechanika/ is approved.

• Maintenance rule

  • Adds an explicit instruction to keep this README section updated with current status, next steps, and blockers as the project evolves.

[Copilot]

Pull request overview

Adds a standing “Co dalej?” (What next?) onboarding section to the README to capture current project status and actionable next steps for a new maintainer in Sprint 0.

Changes:

• Replaces the previous “Next step” section with a new “Co dalej?” section describing Sprint 0 status and an ordered onboarding flow.
• Lists the first docs to read and reiterates the intended Copilot slash-command workflow/order.
• Adds an explicit maintenance instruction to keep this section updated with current status, next steps, and blockers.