feat: reach the rest of Gitea with kettle api, and drop tea

The plugin required `tea`, Gitea's own CLI, for everything that is not an
issue: releases, pull requests, milestones, branches, actions, webhooks. That
put a second binary, a second set of logins nothing here could see, and 400
lines documenting somebody else's flags outside anything this repository can
test. One command over the transport that already existed removes all three.

Transport: `post` — the hand-rolled request the SDK cannot express, written for
the dependency endpoint — is generalized to an exported `Do`, and `post` is
three lines on top of it. Same http.Client, so the same RoundTripper files the
body under .kettle/payload/, the same `token …` header authenticates it, and a
non-2xx is the same *APIError. It does not paginate, does not reformat the
answer, and names no domain concept, so the layering test is untouched.

The endpoint rule is `tea api`'s, so an endpoint table written for that tool
still works — with one restriction it did not have: a full URL must be on this
instance. Every request carries the project's token in a header, and a URL on
another host would hand the token to whatever was typed.

Command: `kettle api <endpoint>` in a new `api` group, so the generator writes
plugins/kettle/skills/api/SKILL.md — group, directory and /kettle:api are one
word. No --repo and no --login, for the reason no sync command has them: a
cross-repository address is an address, and another instance is KETTLE_URL.
`-X DELETE` needs `--yes`; a flag typed on purpose is an operator's decision.

Scopes: a token minted for issues carries write:issue and answers 403 on the
first request outside issues, naming no scope. Gitea cannot be asked what a
token may do — its own token listing needs a password — so `auth add --scopes`
records it, `auth list` and `config` show it, and a 403 says which category it
is likely to be. Documentation only; nothing is checked against it.

skills/use — the tea reference, 239 lines of it — becomes skills/api: what to
ask for, which endpoints paginate, and how to write a body. Every mention of
`tea` as a requirement is gone from the manifests, the READMEs, the runner and
the four other skills; what survives is the back-compat with the old plugin,
which is a decision and not a debt.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -13,7 +13,7 @@ Where to go from here, and each of these directories documents itself:
 
 | directory | what it is |
 |---|---|
-| [`cli/`](cli/AGENTS.md) | one Go module, two binaries: `kettle`, which owns every mechanical thing about issues — the format, the store, the credentials, the tracker — and [`cmd/release`](cli/cmd/release/AGENTS.md), which publishes this repository's own releases. `make check` is the gate; there is no CI here |
+| [`cli/`](cli/AGENTS.md) | one Go module, two binaries: `kettle`, which owns this project's connection to its tracker — the format, the store, the credentials, the transport, and through `kettle api` every Gitea entity that has no command of its own — and [`cmd/release`](cli/cmd/release/AGENTS.md), which publishes this repository's own releases. `make check` is the gate; there is no CI here |
 | [`plugins/`](plugins/AGENTS.md) | what a plugin is here, and what the catalog entry has to match |
 | [`plugins/kettle/`](plugins/kettle/AGENTS.md) | the plugin that wraps the binary: skills, the runner subagent, the hooks |
 | [`plugins/tdl/`](plugins/tdl/AGENTS.md) | the Three Dots Labs Go rule set — no binary, no state, just rules and templates |
@@ -23,6 +23,14 @@ worth carrying: **a binary holds what can be enforced, a plugin holds what can
 only be stated.** Anything mechanical belongs in Go where a test can hold it
 down; anything that is a judgement an operator makes belongs in a SKILL.md.
 
+`kettle api` is that rule applied to an external dependency rather than to a
+script. Reaching a release or a pull request used to mean requiring `tea`, which
+put the credentials, the request and the flags outside anything this repository
+could test — so the mechanical half came in as one command over the transport
+that already existed, and what stayed in the plugin is the half that was never
+mechanical: which endpoint answers the question, and whether the thing should be
+deleted at all.
+
 ## The AGENTS.md convention
 
 **Every directory with a story documents itself, in that directory.** This file