Skill manager: view, add, edit, and link skills across every harness

[n0mahd]

Problem

Skills live in a different directory for every harness: ~/.claude/skills, ~/.agents/skills, <repo>/.claude/skills, <repo>/.agents/skills, ~/.pi/agent/skills, and so on. Users who move between providers end up with duplicated copies that drift apart, or skills that one harness sees and another doesn't. T3 Code already scans every one of these locations per provider for the $ picker, but there's no way to see the gaps or fix them (see #6987, #6883).

Proposal

Revive #4630's read-only Settings → Skills page and extend it to every supported provider (Claude, Codex, Cursor, Grok, OpenCode, Antigravity, Pi), with a small set of actions:

• View: skills grouped by user scope and by project, with per-harness coverage (which harnesses actually load it), its source (one real copy, a symlink, or a drifted duplicate) and the rendered SKILL.md. One view per connected environment, so multi-machine setups can compare.
• Add: create a SKILL.md in the Agent Skills standard location, .agents/skills/, at user scope or project scope.
• Edit: a SKILL.md editor that saves to the symlink's resolved target, so editing a linked skill edits its source.
• Link into all harnesses: symlink the skill into each harness directory that doesn't read .agents/skills (for example .claude/skills/<name>, the same pattern this repo already uses). It never overwrites a real directory. Same-name duplicates with different contents are shown as conflicts for the user to resolve. Precedence is keyed by (scope, location, directory), not by name, per the edge case raised in [Feature]: Discover repo-local `.agents/skills` (Agent Skills standard) provider-agnostically, not per provider #6883.
• Reverse: unlink from one harness, and delete a skill with confirmation.

Server-side these are service methods behind the existing environment auth, so MCP tools for agents are a small follow-up.

Out of scope for the first PR: a mobile UI, MCP tools, marketplace or remote installs, and copying skills between machines (git or dotfiles already do that).

Question for maintainers: would you accept a PR with this scope, or would you rather it ship as a read-only view first with editing and linking as a second PR? I'm happy to share a working prototype in this thread for feedback on the UX before opening anything.

[Yuruzuu]

This would actually be very nice. I'd love to see it at some point with MCP servers being editable per provider too :)

[Jdreioe]

It would be very nice