feat(web): configurable peer display name

Human peers surface as raw ids (WhatsApp `…-lid`, UUIDs). Read an
optional `display_name` from peer metadata and prefer it over the id in
the peer header and breadcrumb, with the raw id kept as a sub-caption.
An inline edit on the header writes `display_name` via useUpdatePeer
(merging existing metadata); blank clears it. Falls back to the id when
unset.

Closes #32.

packages/web/src/lib/peerDisplay.ts

@@ -0,0 +1,25 @@
+/**
+ * Resolve a peer's friendly display name from its metadata, falling back to the
+ * raw peer id. Honcho peers are keyed by opaque ids (WhatsApp `…-lid`, UUIDs);
+ * a `display_name` metadata key lets the UI show something human-readable.
+ */
+export const DISPLAY_NAME_KEY = "display_name";
+
+export function peerDisplayName(
+	metadata: Record<string, unknown> | null | undefined,
+	fallbackId: string,
+): string {
+	const value = metadata?.[DISPLAY_NAME_KEY];
+	if (typeof value === "string" && value.trim().length > 0) {
+		return value.trim();
+	}
+	return fallbackId;
+}
+
+/** Whether a peer has an explicit display name distinct from its id. */
+export function hasDisplayName(
+	metadata: Record<string, unknown> | null | undefined,
+	peerId: string,
+): boolean {
+	return peerDisplayName(metadata, peerId) !== peerId;
+}