chore(vendor): import pi 1.3.0

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: 71023aec1546d6d677a65669c5665c0927ce0dd0

third_party/pi/packages/chord/src/registry.ts

@@ -0,0 +1,30 @@
+import type { Ctx } from "./types.ts";
+
+export interface Registry<V> {
+	readonly name: string;
+	readonly conflict: "error" | "last";
+	/** Type carrier only; never set. */
+	readonly value?: V;
+}
+
+/** `conflict: "error"` rejects two objects registering one key; `"last"` keeps the later registration. */
+export const defineRegistry = <V>(name: string, options: { conflict?: "error" | "last" } = {}): Registry<V> => ({
+	name,
+	conflict: options.conflict ?? "error",
+});
+
+export type RegistryTable<V> = ReadonlyMap<string, V>;
+
+export interface RegistryView<V> {
+	/** Table of `ctx.codeVersion`, or of the current code version without ctx. */
+	table(ctx?: Ctx): RegistryTable<V>;
+	get(key: string, ctx?: Ctx): V | undefined;
+	/** Called with the current table immediately and whenever a new table is installed. */
+	subscribe(listener: (table: RegistryTable<V>, codeVersion: number) => void): () => void;
+}
+
+export interface Registration {
+	readonly registry: Registry<unknown>;
+	readonly key: string;
+	readonly value: unknown;
+}