Restructure tea skill into a plugin with a mandatory-login guard

Convert the standalone `tea` skill into a skills-dir plugin so commands are
namespaced and an enforcement hook can ship with it:

- /tea:login  — pin the project Gitea login into .claude/settings.local.json
- /tea:use    — tea CLI reference (was the old root SKILL.md), with the
                login rule slimmed since the hook now enforces it
- hooks/tea-guard.sh — PreToolUse(Bash) guard: blocks any `tea` command that
  touches Gitea unless it carries --login and $GITEA_LOGIN is set. Exempts
  `tea logins list` and `tea --version/--help` so /tea:login can bootstrap.

References moved under skills/use/references/. `claude plugin validate` passes;
guard unit-tested across allow/block cases.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

skills/use/references/tea/helpers.md

@@ -0,0 +1,30 @@
+# tea CLI — HELPERS
+
+See [`./index.md`](./index.md) for global options and common flags shared by all commands.
+
+## `tea open, o`
+Open the current repository/context in a web browser.
+
+## `tea notifications` (aliases: `notification`, `n`)
+Defaults to the current repo; `--mine/-m` aggregates across all your repos. Fields: `id,status,updated,index,type,state,title,repository`. Filters: `--types/-t {issue|pull|repository|commit}`, `--states/-s {pinned|unread|read}` (default: `unread,pinned`).
+
+- `ls, list`
+- `read, r [all | <id>]`
+- `unread, u [all | <id>]`
+- `pin, p [all | <id>]`
+- `unpin [all | <id>]`
+
+## `tea clone, C <repo-slug> [target-dir]`
+Clone without requiring a local git install. Accepts slug forms: `gitea/tea`, `tea`, `gitea.com/gitea/tea`, `git@gitea.com:gitea/tea`, `https://gitea.com/gitea/tea`, `ssh://gitea.com:22/gitea/tea`. A host in the slug overrides `--login`. Options: `--depth/-d`, `--login/-l`.
+
+## `tea api <endpoint>`
+Authenticated HTTP request to the Gitea API. Endpoints are auto-prefixed with `/api/v1/` unless they start with `/api/` or `http(s)://`. Placeholders `{owner}` and `{repo}` are filled from the repo context.
+
+- `--method/-X {GET|POST|PUT|PATCH|DELETE}` (default GET; switches to POST automatically when a body is provided)
+- `--field/-f key=value` — string field on body (repeatable).
+- `--Field/-F key=value` — typed field (numbers, booleans, null, JSON arrays/objects); `@file` or `@-` (stdin); `"null"` forces literal string.
+- `--data/-d` — raw JSON body (`@file` / `@-`). Incompatible with `-f`/`-F`.
+- `--header/-H key:value` (repeatable)
+- `--include/-i` — write status + response headers to stderr.
+- `--output/-o <file>` — write response body to file (`-` = stdout).
+- Quote the endpoint if it contains `?` or `&` to prevent shell expansion.