Feature request: programmatic upload of custom skills to claude.ai (API or CLI)

## Summary

There is no programmatic way to upload or update a custom skill on a claude.ai account. The only path is the Settings > Capabilities > Skills > Add skill > Upload skill dialog, which takes a .zip through a browser file input.

## Why it matters

Claude Desktop's Cowork surface does not read `~/.claude/skills`. It syncs the account's enabled skills into an app-managed folder (`local-agent-mode-sessions/skills-plugin///skills/`) and the sync removes anything it did not download ("orphans cleaned" in the desktop log). So a skill authored and tested in Claude Code has to be re-zipped and pushed through the web dialog every time it changes before Cowork can use it.

For teams that keep skills in git and iterate on them, that means:

- No CI or script can publish a skill on merge.
- Claude Code itself cannot promote a local skill to the account, even when the user asks it to. Today I had Claude Code zip a skill and drive the claude.ai upload dialog through the Chrome extension, which works but is fragile.
- Two copies drift: the local `~/.claude/skills` copy that Claude Code reads and the account copy that Cowork reads.

## Request

Any of these would solve it:

1. A REST endpoint for skills on the claude.ai account (create, update, delete, list), authenticated the same way connectors are.
2. A `claude skill push ` (or `claude skill upload`) CLI command that zips a skill directory and publishes it to the signed-in account.
3. Have Cowork read `~/.claude/skills` in addition to account skills, so a local skill is usable on both surfaces without a round trip through the web UI.

Option 2 fits the existing CLI shape and would let a git hook or GitHub Action publish on merge.

## Environment

- Claude Code 2.1.266, Claude Desktop (macOS) Cowork
- Observed 2026-09-09

Start by mapping the existing CLI command surface and the connector authentication path mentioned in the request, then compare them with the claude.ai Skills upload flow. The scope still needs a decision between a REST API, a new skill upload command, or Cowork local-skill support. Done means the selected path can publish or use an updated skill without the browser upload dialog.

索引モデルが issue の本文から書いたものです。