Phase 6: track per-platform Skill install convention drift

[thomaschristory]

Phase 5 spec §1.2 — deferred to Phase 6+.

Skill install automation refinements. Per-platform install paths may evolve; nsc skill install will need refresh per platform release.

Scope

A recurring (suggest quarterly) review of the four target conventions
hard-coded in nsc/cli/skill_commands.py:_RESOLVERS:

• claude-code → ~/.claude/skills/<name>/SKILL.md (confirmed 2026-05-06 via https://code.claude.com/docs/en/skills)
• codex → ~/.agents/skills/<name>/SKILL.md (confirmed 2026-05-06 via https://developers.openai.com/codex/skills; this is the agent-tool-neutral path documented at the canonical Codex docs URL — NOT the originally-hypothesized ~/.codex/skills/)
• gemini → MANUAL (no programmatic Skill loader documented as of 2026-05-06)
• copilot → MANUAL (no programmatic Skill loader documented as of 2026-05-06; the new GitHub Copilot CLI replaced the deprecated gh-copilot extension on 2025-10-25 but does not yet expose a ~/.copilot/skills/ path)

Why deferred from v1

v1 ships the snapshot above. Convention drift is a maintenance pattern, not a v1 deliverable.

Acceptance

• A quarterly maintainer task (issue or calendar reminder) re-checks each canonical URL above.
• If any platform flips MANUAL → confirmed (or an existing path moves), the resolver in nsc/cli/skill_commands.py, the path table in docs/guides/using-with-ai-agents.md, and the SKILL.md "What's installed" section are updated in one PR with a CHANGELOG entry.
• Suggested first review date: 2026-08-06 (3 months after v1.0.0).