feat(skills): add per-profile skills management

[cooco119]

Summary

• Add skills_mode (shared | isolated) to account config, enabling per-profile skill isolation
• Implement syncSkills() in SharedManager that converts the instance skills/ symlink to a real directory with individually symlinked shared skills
• Add ccs skills <profile> <command> CLI that wraps npx skills with CLAUDE_CONFIG_DIR targeting the correct instance directory
• Auto-isolate on ccs skills <profile> add, sync shared skills during ccs sync

How it works

When skills_mode: isolated is set for an account profile:

1. The instance's skills/ symlink (→ shared → ~/.claude/skills) is replaced with a real directory
2. Each shared skill from ~/.claude/skills/ is individually symlinked into the instance directory
3. npx skills add -g runs with CLAUDE_CONFIG_DIR pointing to the instance, so new skills install directly into the isolated directory
4. Profile-specific skills coexist with shared skill symlinks

Changed files

File	Change
src/auth/account-context.ts	AccountSkillsMode type, skillsMode in policy/metadata
src/config/unified-config-types.ts	skills_mode on AccountConfig
src/types/config.ts	skills_mode on ProfileMetadata
src/management/shared-manager.ts	syncSkills() + syncSharedSkillsToIsolated()
src/management/instance-manager.ts	Call syncSkills() in ensureInstance()
src/commands/sync-command.ts	Sync isolated skills during ccs sync
src/commands/skills-command.ts	New — CLI wrapping npx skills
src/ccs.ts	Route skills subcommand
src/commands/help-command.ts	Per-Profile Skills help section
tests/unit/skills-sync.test.ts	New — 7 tests for syncSkills

Test plan

• bun run format — clean
• bun run typecheck — no errors
• bun run lint:fix — clean
• bun run validate — exit 0 (pre-existing failures unrelated)
• bun run validate:ci-parity — passed (pre-push hook)
• 7 new tests pass (skills-sync.test.ts)
• 34 related tests pass (account-context, shared-context-policy, shared-manager, sync-command)
• Manual: ccs skills personal isolate → ccs skills personal add <pkg> → ccs skills personal list
• Manual: ccs skills personal share restores shared mode
• Manual: ccs sync preserves isolated skills

🤖 Generated with Claude Code