feat(plugin): serve Loop as a proxy stub

Composer::getLoop() answers, so a plugin reaches the graph's own downloader
and executor through the route Composer's own docblocks point plugin authors
at, rather than through an instance of its own.

wait() drains the promises it is given and rethrows the first rejection once
the group is done, which is what React\Promise\all() hands PHP. abortJobs()
has nothing to cancel while every request settles before the call that
started it returns. A non-null $progress is an explicit error: a ProgressBar
is a symfony/console object each world runs its own implementation of, so
there is none to hand across.

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

1 files changed, 8 insertions, 4 deletions

diff --git a/docs/dev/plugin-class-classification.md b/docs/dev/plugin-class-classification.md
index 5cb8fd6e..fd6102f3 100644
--- a/docs/dev/plugin-class-classification.md
+++ b/docs/dev/plugin-class-classification.md
@@ -432,10 +432,14 @@ resolves its promise with a `Symfony\Component\Process\Process`, whose state
 is the `proc_open()` resource of whichever process called `start()`; a request
 resolves its promise with a `Response`, which is data.
 
-`Loop` remains guarded, so `Composer::getLoop()` is still an explicit error
-and neither the graph's own executor nor its downloader is reachable through
-it. Serving it needs only a `Loop` stub, since both surfaces it hands out are
-already served.
+`Loop` is a proxy stub too, so `Composer::getLoop()` — the route Composer's own
+docblocks point plugin authors at — reaches the graph's own downloader and
+executor. Its `wait()` drains the promises it is given and rethrows the first
+rejection once the group is done, which is what `React\Promise\all()` hands
+PHP; `abortJobs()` has nothing to cancel while every request settles before the
+call that started it returns. A non-null `$progress` is an explicit error: a
+`ProgressBar` is a symfony/console object each world runs its own
+implementation of, so there is none to hand across.
 
 ### Dual instantiation