🔥Remove stream combinators

Stream transformations are not our core competency. If Effection is
measured by that yard stick, it'll come up short because what we have
is 5% implementation of a not-strongly-opinionated stream helpers
library. One could very reasonably ask "well where is flatMap(),
merge(), reduce(), reduceRight()" and on and on. The answer is that we
aren't in that business, and it's better to not play that game at all,
than to enter the race and get lapped 20 times.

Our mantra is "Structured Concurrency and Effects for
JavaScript". It's a minimalist approach that seeks to excel via
maximum compatibility and minimum friction over the long term. Having
these as part of our API surface feels like it runs counter to that
principle.

In the spirit of keeping things "core", remove first(), filter(),
map(), pipe(), and associated documentation.

They should be published as a separate library where the optimal
implementation (if there is one) can be discovered.

lib/events.ts

@@ -1,7 +1,6 @@
 // deno-lint-ignore-file no-explicit-any ban-types
 import { createSignal } from "./signal.ts";
 import { resource } from "./instructions.ts";
-import { first } from "./mod.ts";
 import type { Operation, Stream, Subscription } from "./types.ts";
 
 type FN = (...any: any[]) => any;
@@ -32,7 +31,13 @@ export function once<
   T extends EventTarget,
   K extends EventList<T> | (string & {}),
 >(target: T, name: K): Operation<EventTypeFromEventTarget<T, K>> {
-  return first(on(target, name));
+  return {
+    *[Symbol.iterator]() {
+      let subscription = yield* on(target, name).subscribe();
+      let next = yield* subscription.next();
+      return next.value;
+    },
+  };
 }
 
 /**

lib/mod.ts

@@ -5,13 +5,9 @@ export * from "./instructions.ts";
 export * from "./call.ts";
 export * from "./run.ts";
 export * from "./sleep.ts";
-export * from "./first.ts";
 export * from "./async.ts";
 export * from "./abort-signal.ts";
 export * from "./result.ts";
-export * from "./map.ts";
-export * from "./filter.ts";
-export * from "./pipe.ts";
 export * from "./lift.ts";
 export * from "./events.ts";
 export * from "./main.ts";