Align Copilot prompt commands and clean up Sprint 0 onboarding docs

[Copilot]

The README “Next step” section pointed users to slash commands that do not exist at runtime, which made the documented onboarding path fail immediately. This change audits the repo’s setup docs and aligns all prompt references with how Copilot actually resolves custom prompt commands.

• Fix broken prompt invocation docs

  • Replaced '/prompt-*' references with the actual command names exposed by prompt frontmatter, e.g. '/game-dev', '/skills-adoption', '/new-scene'.
  • Updated prompt file headings to match the real slash commands for consistency across docs and prompt assets.

• Repair README onboarding path

  • Reworked README.md “Next step” into a usable Sprint 0 entry point.
  • Added a compact fallback path for cases where custom prompts do not appear in VS Code.
  • Made the current repo state explicit: docs-first, no package.json, no src/, no runnable app commands yet.

• Sync cross-repo documentation

  • Updated docs/COPILOT_WORKFLOW.md, .github/copilot-instructions.md, and SKILLS_RECOMMENDATIONS.txt to use the same command vocabulary.
  • Updated docs/ARCHITECTURE.md to reflect the actual prompt inventory and removed the stale src/state structure reference.

• Improve newcomer readability

  • Added short English summaries to Polish-only entry docs that the README sends users to, reducing the language cliff at first contact.

Example of the corrected command mapping:

# before
/prompt-game-dev
/prompt-new-scene Boot

# after
/game-dev
/new-scene Boot

[Copilot]

Pull request overview

This PR fixes broken Sprint 0 onboarding by aligning all documentation and prompt assets with how GitHub Copilot actually exposes custom slash commands (via each prompt file’s YAML name:), removing stale /prompt-* references that would fail at runtime.

Changes:

• Replaced outdated /prompt-* command references across README/docs with the real commands (/game-dev, /skills-adoption, etc.).
• Updated prompt file headings and architecture docs to reflect the actual prompt inventory and command naming source (name: field).
• Improved newcomer onboarding by adding brief English summaries to Polish-first docs referenced during Sprint 0.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
SKILLS_RECOMMENDATIONS.txt	Updates the documented adoption mechanism to use the correct /skills-adoption command.
README.md	Repairs the Sprint 0 “Next step” onboarding path and adds troubleshooting guidance for missing slash commands.
mechanika/README.md	Adds an English summary to reduce the language cliff for mechanics-spec onboarding.
docs/COPILOT_WORKFLOW.md	Aligns the workflow guide with actual slash commands and adds a concise English summary.
docs/ARCHITECTURE.md	Documents the correct source of slash command names and updates the prompt inventory/tree.
.github/prompts/skills-adoption.prompt.md	Updates the prompt’s visible heading to match the actual /skills-adoption command.
.github/prompts/pwa-check.prompt.md	Updates the prompt’s visible heading to match /pwa-check.
.github/prompts/new-system.prompt.md	Updates the prompt’s visible heading to match /new-system.
.github/prompts/new-scene.prompt.md	Updates the prompt’s visible heading to match /new-scene.
.github/prompts/new-event.prompt.md	Updates the prompt’s visible heading to match /new-event.
.github/prompts/mobile-ux.prompt.md	Updates the prompt’s visible heading to match /mobile-ux.
.github/prompts/game-dev.prompt.md	Updates the prompt’s visible heading to match /game-dev.
.github/prompts/data-schema.prompt.md	Updates the prompt’s visible heading to match /data-schema.
.github/prompts/code-review.prompt.md	Updates the prompt’s visible heading to match /code-review.
.github/copilot-instructions.md	Aligns workflow command references and documents that commands come from prompt name: frontmatter.