feat: hs skill install — bundle the hearthstone-deck skill with the CLI

[say8425]

Summary

Adds a channel-agnostic way to install the hearthstone-deck Claude Code skill alongside the hs CLI, plus publishes/advertises it cross-agent. Implements the D + C + B design (spec + plan committed under docs/superpowers/).

D — hs skill install subcommand

• Installs the embedded skill into agent skills dirs: claude, cursor, codex, copilot, opencode (matches the npx skills directory convention). --global (default) or --project.
• Skill files (SKILL.md + recipes) are embedded into the binary via Bun text imports — no network, no Node/npx needed (preserves the brew/binary "no runtime" benefit). Single source of truth stays at plugins/hs-cli/skills/hearthstone-deck/; a test asserts byte-equality between bundle and disk.
• Interactive @clack/prompts multiselect (rendered to stderr so -f json stdout stays pipeable) or non-interactive --agent claude,cursor. Non-TTY without --agent → guard error + exit 1 (safe for agents that pipe the CLI).
• Hybrid --use-npx: short-circuits to npx skills add say8425/hs-cli when npx is available.
• Convergent project targets (cursor/codex/copilot/opencode all map to .agents/skills) are de-duplicated — one install + one outcome per physical dir.

C — skills.sh publishing

• Verified npx skills add say8425/hs-cli discovers hearthstone-deck via the existing .claude-plugin/marketplace.json layout. Zero restructure needed.

B — advertise (no new files)

• brew formula gains a caveats block (in release.yml formula render); install instructions added to all READMEs (en/ko/ja/zh/es + plugin README). No new README (would duplicate SKILL.md).

Architecture

Four focused pure services + a thin citty command:

• agent-dirs.ts — agent→directory map + path resolver
• skill-bundle.ts — embedded skill files
• skill-installer.ts — pure fs writer (writeBundle, skillExists)
• skill-select.ts — pure selection resolver (validation + non-TTY guard)
• commands/skill.ts — clack/npx I/O glue; output via formatSkillOutcomes in formatter.ts

Test Plan

• bun run check — lint (0 errors), fmt:check, tsc, 58 tests pass
• e2e: non-TTY guard exits 1; embedded install into temp dirs (claude+cursor); idempotent --force; node-target build (dist/index.js) carries embedded skill files (EMBED OK)
• convergent --agent claude,cursor,codex --project → 2 outcomes, not 3
• npx skills add say8425/hs-cli --list discovers hearthstone-deck
• CI: 5-platform compiled binaries run hs skill install (compiled-binary execution not runnable locally on macOS codesign; validated on node target + bundler embed)

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