Integrate and plan fusion of SIN-Shop-Center skills

[Delqhi]

Goal

Integrate the shop-related skills from SIN-Shop-Center into the SIN-Code bundled skill catalog and plan their long-term fusion strategy.

What Already Exists

• SIN-Code/skills/shop-skills/cj-dropshipping/ (bundled doc)
• SIN-Code/skills/shop-skills/stripe/ (bundled doc)
• SIN-Code/skills/shop-skills/tiktok-shop/ (bundled doc)
• Validation script was updated to support one-level nested skill categories.

Source Repos to Fuse

Bundled Skill	Source Repos	Current State
cj-dropshipping	OpenSIN-Code/cj-dropshipping-skill + SIN-Shop-Center/SIN-CJDropshipping-Bundle	bundled doc only, external implementation
stripe	SIN-Shop-Center/SIN-Stripe-Bundle	bundled doc only, external implementation
tiktok-shop	SIN-Shop-Center/SIN-eCommerce-Scraper-Bundle (TikTok Shop part)	bundled doc only, external implementation

Long-Term Strategy

Follow the canonical skill lifecycle:

1. Phase 1 — external implementation stays canonical until a native sin-code subcommand exists.
2. Phase 2 — bundled SKILL.md docs are the offline reference (already done for the three shop skills).
3. Phase 3 — implement native sin-code cj, sin-code stripe, sin-code tiktok-shop subcommands when the shop domain matures.
4. Phase 4 — deprecate the external repos once native implementations are stable.

Immediate Tasks

• Add lifecycle: external to the frontmatter of the three shop skills.
• Add sources frontmatter entries pointing to the canonical external repos.
• Register the shop skills in mcpclient/registry.go and skillmgr.KnownSkills() if they should be installable via sin-code skill install.
• Decide whether SIN-Shop-Center/SIN-eCommerce-Scraper-Bundle should be split into dedicated tiktok-shop-skill and cj-dropshipping-skill repos, or kept as a bundle.
• Populate context/, frameworks/, tasks/, templates/ with minimal .md content so strict validation has no empty-dir warnings.

Acceptance Criteria

• python3 scripts/validate_skill.py --all-bundled --strict passes.
• sin-code skills list shows the three shop skills under their category (or flat).
• The three SKILL.md files clearly state that the canonical implementation is external and point to the source repos.

[Delqhi]

Closed: shipped in PR #221 (feat(skillmgr): register shop skills in KnownSkills, issue #142 fusion). The bundled SKILL.md files already had lifecycle: external + sources: frontmatter from PR #218 (issue #139). The registry half of #142 is now in cmd/sin-code/internal/skillmgr/manager.go: shop-cj-dropshipping, shop-stripe, shop-tiktok. Long-term fusion strategy documented in the issue body: phase 1 (external) → phase 2 (bundled doc) → phase 3 (native subcommand) → phase 4 (deprecate upstream).