feat(cli): extract playlists end to end from the command line

[cmglezpdev]

What this changes

veta <playlist-url> now works end to end: auto-detected on the extract command, [k/n] <title> member progress and an end-of-run summary on stderr, exactly one line on stdout (the playlist prompt.md path) printed before any partial-failure exit (code 9; empty playlist exits 6), playlist-grouped list output, and the interactive clipboard offer after playlist runs. Documents playlist usage in README and roadmap.

Why

Final integration slice of increment 1 — everything user-visible.

How to verify

pnpm typecheck
pnpm vitest run src/cli --exclude '**/.claude/**'
node bin/veta.js "https://youtube.com/playlist?list=PL9omX6impEuMgDFCK_NleIB0sMzKs2boI"
node bin/veta.js list

Manually verified against that 13-video playlist (all extracted, resume works, clipboard offer appears in a TTY).

Checklist

• pnpm typecheck and pnpm test pass
• Commits follow Conventional Commits

Scope

• Includes: CLI wiring, progress renderer prefixes, exit-code wiring, list grouping with de-duplication, purge regression proof, docs.
• Excludes: curation flags (follow-up PRs); --lang passthrough on playlist runs (known gap, currently inert — follow-up).

Chain Context

Field	Value
Chain	playlist-support
Tracker PR	#40
Position	6 of 6
Base	feat/playlist-support-04-orchestrator
Depends on	PR 5 (#45)
Follow-up	curation flags (follow-up)
Review budget	645 / 400

Chain Overview

main
 └── #40 tracker: feat/playlist-support
      └── #41 listing → #42 store → #43 packageName → #44 prompt → 04 orchestrator → 05 CLI
          (this PR: 📍 6)