Reverts the previous round's choice of embedding an ObservableEventStore
inside EventStore. The wrapper now lives strictly outside any specific
store: callers compose `ObservableEventStore(EventStore(...))` (or
`ObservableEventStore(FsEventStore(...))`, or any IEventStore) and use
that as their projection bus.
EventStore is back to a plain IEventStore implementation over
SQLiteEventStore — no `observable`, `events`, or `observe()` on it.
ObservableEventStore gains the `observe(filters, relay, scope)` and
`observe(filter, relay, scope)` convenience methods. NIP-62 vanish
scoping is passed in per-projection (rather than a constructor field
on the wrapper) so the same observable can feed projections with
different relay scopes.
Tests construct `observable = ObservableEventStore(store)` in
`setUp` and route inserts through `observable.insert(...)` so the
projection bus actually publishes them. 14/14 projection + 219/219
other store tests pass.
https://claude.ai/code/session_01Jny85MTu1ynKgFBgysfWu5
Claude
32850c3d40