v0.7.0

One break, and it is the one this library most needed to make before anyone
depended on it (ADR-0047).

Hooks are the rules that confine what a query may see, so they were also the
one surface where ambient state could decide a tenant boundary. OnT
registered into a package-level default, New(exec) handed every handle that
same default, and OnInT — the form that says where the rules land —
carried the longer name. compatibility.md had listed the hazard under "Will
move" for two releases, in the words it turned out to deserve: which registry a
statement uses is decided by the dynamic type of the executor passed to it.

What made it a release rather than a note is that it cost an adopter a tenant
boundary. Moving an application onto a per-application registry left one module
still calling OnT, so that module's rules were no longer on the handle it
queried through — and it still compiled, still mounted, and still answered,
with every tenant's rows in the response. Both spellings were valid, and the
wrong one was shorter.

So the default is gone. sqlb.New gives each handle an empty registry of its
own, OnT is the only registration form, rest.PublishChanges[T](r, p) takes
the registry too, and an Executor that is not a *sqlb.DB resolves to a registry
nothing can register into — a statement against a bare pool is unconfined, and
says so.

The mechanical edit, and every one of them is a compile error rather than a
behaviour change, which is the point: the failure this prevents is silent, so
its migration must not be.

On[T]()               ->  On[T](reg)
OnIn[T](reg)          ->  On[T](reg)
PublishChangesIn[T]   ->  PublishChanges[T]
sqlb.New(pool)        ->  sqlb.New(pool).WithHooks(reg)

There is no shim, because a shim is the ambient registry under a new name.

What goes with the default is its bookkeeping. Hooks.Reset survives with its
reason rewritten — a test gets isolation from NewRegistry, which cannot be
forgotten in a teardown — and the sync.Once guards, t.Cleanup(Reset) pairs and
"has anything registered yet?" checks that existed to manage a registry nobody
asked for are deleted. The examples had all left already, which is the tell:
example/tasks built its own registry and said why, and the fx kit never used
the default at all.

What this does not fix, named in the record rather than discovered later: a
registry nothing attaches. OnT compiles whether or not any handle
carries reg, so hooks can still be registered where nothing runs them. That is
strictly narrower — the registry and the handle are usually adjacent
expressions rather than action at a distance — and the case that matters is
still caught at the mount, because a model declaring Scoped is refused when the
handle's registry has no hook for it (ADR-0030).