docs(adr): compress to 1 record in the domain-modeling format

docs/adr/0001-own-the-lifespan-composition.md

@@ -1,31 +1,11 @@
-# The lifespan composition is ours; FastAPI's `_merge_lifespan_context` is not used
-
-**Decision:** `setup_di` installs the container's open/close onto the public
-`app.router.lifespan_context` through this package's own `_compose_lifespan`. It does not call
-`fastapi.routing._merge_lifespan_context`, which it used until 2.8.0.
-
-The obvious objection is that FastAPI already ships lifespan composition, so writing our own is
-duplicated work over a name that has been stable for years. Two things answer it.
-
-**It is private, and the supported FastAPI range is enormous.** `pyproject.toml` pins
-`fastapi>=0.100,<1`. A leading-underscore name in `fastapi.routing` carries no compatibility
-promise across that range, and the failure mode is an `ImportError` at `setup_di` time — every app
-using this package, at startup, on a routine FastAPI upgrade.
-
-**It does not do what we need anyway.** `_merge_lifespan_context` composes two *lifespans* —
-`Callable[[App], AsyncContextManager]` — and yields `{**nested, **original}` from their two states.
-A `Container` is a bare async context manager yielding nothing, so it would first have to be wrapped
-in a lifespan-shaped callable, which is most of `_compose_lifespan` already; and the merge path
-would then replace the original lifespan's own passthrough — its `None` or its mapping, verbatim —
-with a freshly built dict. That is a behaviour change to the user's lifespan in exchange for
-borrowing seven lines.
-
-What `_compose_lifespan` owns beyond wrapping is the one thing neither helper would give us: it
-enters the container with `async with` rather than a one-shot open, so a second lifespan cycle
-against the same container reopens it instead of raising `ContainerClosedError` — the case
-`test_lifespan_reopens_container_across_cycles` covers, and the reason repeated `TestClient`
-contexts work against one container.
-
-**Revisit trigger:** Starlette or FastAPI publishes a *public* lifespan-composition helper whose
-state handling is passthrough rather than merge. At that point the wrapper is borrowable and
-`_compose_lifespan` should shrink to the `async with` that reopens the container.
+# The lifespan composition is ours
+
+`setup_di` installs the container's open/close onto the public `app.router.lifespan_context` through
+this package's own `_compose_lifespan`, not through `fastapi.routing._merge_lifespan_context`, which
+it used until 2.8.0. That helper is private while `pyproject.toml` pins `fastapi>=0.100,<1`, so a
+rename anywhere in that range is an `ImportError` at `setup_di` time, at startup, for every app on a
+routine FastAPI upgrade. It also composes two lifespans and merges their yielded states, while a
+`Container` is a bare async context manager yielding nothing: wrapping it into lifespan shape is
+most of `_compose_lifespan` already, and the merge would rebuild the user's state as a fresh dict
+rather than pass it through. Our wrapper also enters the container with `async with`, so a second
+lifespan cycle reopens it instead of raising `ContainerClosedError`.