feat(mod): quest picker for tutorial tracks

[todortodorovic]

Adds an interactive quest browser to dot mod. When a track app's source
repo ships a quests.json at the root on main, the CLI displays the
quest list (id, title, difficulty, dependencies, summary) and waits for
the user to press "Start tutorial" before continuing into the existing
clone flow. Non-track apps incur a single CDN GET (no GitHub API quota)
and skip the picker silently.

What's new

• src/utils/mod/quests.ts — manifest fetch (raw.githubusercontent.com,
  always main), parser with schema validation, findQuest lookup.
• src/commands/mod/QuestPicker.tsx — read-only Ink list with cursor
  navigation, summary preview for the focused quest, and a "Start
  tutorial" button. ⏎ continues, q cancels.
• src/commands/mod/index.ts — hook between the public-repo check and
  the existing runSetup. Pre-fetches metadata on the direct-domain path
  so both dot mod <domain> and the interactive picker show the
  manifest.

[github-actions]

Dev build ready — try this branch:

curl -fsSL https://raw.githubusercontent.com/paritytech/playground-cli/main/install.sh | VERSION=dev/quest-path bash

[github-actions]

E2E Test Pass · ❌ FAIL

Tag: e2e-ci-pr · Branch: quest-path · Commit: c009ff4 · Run logs

Cell	Result	Time
pr-deploy-foundry	✅ PASS	0m38s
pr-install	✅ PASS	0m41s
pr-deploy-frontend	✅ PASS	3m25s
pr-mod	❌ FAIL	10m17s
pr-init-session	✅ PASS	1m54s
pr-deploy-cdm	✅ PASS	2m16s
pr-preflight	✅ PASS	1m17s
${{ matrix.cell }}	⏭️ SKIP	0m00s
${{ matrix.cell }}	⏭️ SKIP	0m-1s

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