Expose author pubkey from e-tag parsing in NoteIdRef

Description: When parsing NIP-10 e-tags, NoteIdRef currently exposes: - id - event ID - relay - relay hint - marker - root/reply/mention Per [NIP-10](https://github.com/nostr-protocol/nips/blob/master/10.md), the full e-tag format includes an optional 5th element for the referenced event's author pubkey: ["e", <event-id>, <relay-url>, <marker>, <pubkey>] ### Current behavior: ``` NoteReply::root() ```and ```NoteReply::reply() ```return NoteIdRef without access to the pubkey, even when it exists in the original tag. ### Requested behavior: Add an optional pubkey field to NoteIdRef: ``` pub struct NoteIdRef<'a> { pub index: u16, pub id: &'a [u8; 32], pub relay: Option<&'a str>, pub marker: Option<&'a str>, pub pubkey: Option<&'a [u8; 32]>, // NEW } ``` Use case: When creating reply notes, clients should preserve the root author pubkey if it was present in the original thread. Currently notedeck cannot do this because NoteIdRef doesn't expose it. ``` // Current: cannot include root author pubkey ["e", "<root-id>", "<relay>", "root"] // Desired per NIP-10: ["e", "<root-id>", "<relay>", "root", "<root-author-pubkey>"] ``` Reference: - NIP-10: https://github.com/nostr-protocol/nips/blob/master/10.md - notedeck relay hints PR: pending ---