feat(tutorial): split mesh tutorials into 3 step categories (Phase 1)

[takaokouji]

Summary

Phase 1 of the tutorial expansion roadmap (#682): split the single CATEGORIES.chatApp (which housed 9 decks = 3 steps × Lv1〜3) into 3 story-themed categories × 3 lv so the tipsLibrary surfaces the step axis and the lv axis as distinct dimensions.

• New categories: meshStep1 ("メッセージを送ってみよう"), meshStep2 ("ふたりで会話しよう"), meshStep3 ("みんなで会話しよう")
• Existing 9 deck IDs are preserved — only category: references and translations are updated
• No new decks, no new images, no behavior change inside individual decks

Also lands the tutorial expansion roadmap (docs/tutorial/improvement-plan.md) covering Phase 1〜4 (Mesh / Ruby / Block / DNCL) and a working progress tracker (docs/tutorial/progress.md) for the multi-phase effort.

Changes

File	Change
packages/scratch-gui/src/lib/libraries/tutorial-tags.js	Remove CATEGORIES.chatApp, add meshStep1/2/3
packages/scratch-gui/src/components/library/library.jsx	Update local messages mapping: remove chatApp label, add 3 new mesh-step labels
packages/scratch-gui/src/lib/libraries/decks/index.jsx	Re-assign category: for 9 chat decks (chat-1-basic-{1,2,3} → meshStep1, chat-2-sprites-{1,2,3} → meshStep2, chat-3-mesh-{1,2,3} → meshStep3)
packages/scratch-gui/src/locales/{en,ja,ja-Hira}.js	Add gui.library.meshStep1/2/3 translations, remove gui.library.chatApp
docs/tutorial/improvement-plan.md	NEW — 4-phase design (Mesh / Ruby / Block / DNCL), setup foundation, puts-centric Ruby strategy, book promotion strategy with Lv0/Lv2/Lv3 numbering
docs/tutorial/progress.md	NEW — progress tracker for the multi-phase rollout (to be deleted when all 4 phases ship)
tools/playwright-verify/verify-tutorial-mesh-categories.mjs	NEW — Playwright script asserting 4 category titles render in tipsLibrary

Verification

bin/dx bash -c "cd packages/scratch-gui && npm run lint"
# → All matched files use Prettier code style!

cd tools/playwright-verify && node verify-tutorial-mesh-categories.mjs
# → [verify] category titles = ["始めましょう","メッセージを送ってみよう","ふたりで会話しよう","みんなで会話しよう"]
# → [verify] OK: all 3 mesh-step categories visible

Screenshot: tools/playwright-verify/tmp/tutorial-mesh-categories.png (gitignored).

Test plan

• CI: lint, unit, integration
• Manual: Open Welcome modal → "最初のチュートリアルを始める" → confirm 4 categories ("始めましょう" + 3 mesh-step) display in story order, each with 3 decks (Lv1/Lv2/Lv3)
• Each deck still opens and progresses (no behavior regression — only category labels changed)
• ja-Hira locale shows hiragana variants ("メッセージをおくってみよう" etc.)

Closes

• Closes feat(tutorial): Phase 1 - Mesh チュートリアルを 3 カテゴリ × 3 lv に再分類 #678

Related

• Parent: feat(tutorial): チュートリアル全体の体系的拡充 (Block / Ruby / Mesh / DNCL) #682 (tracking issue for full tutorial expansion across Phase 1〜4)
• Next: Phase 2 (Ruby, puts-centric, with setup foundation) → feat(tutorial): Phase 2 - Ruby チュートリアル拡充 (TryRuby ベース、puts 中心) + setup 基盤 #679

🤖 Generated with Claude Code

[github-actions]

🚀 Preview deployed: https://smalruby.jp/smalruby3-editor/feature/tutorial-mesh-recategorize/