Add method for determining if `Note` is a network note

[partylikeits1983]

Feature description

In release 0.10.0, we had a convenient Note::is_network_note() method. Since the introduction of NoteAttachments, it’s now more confusing to determine whether a Note is a network note.

Current Behavior

Right now, the simplest approach is:

NetworkAccountTarget::try_from(note.metadata().attachment())

This works, but it’s indirect and not very discoverable.

Proposal

Introduce a NetworkNote newtype wrapper in miden-standards.

This would allow a cleaner API such as:

NetworkNote::try_from(note)

Benefits

• Makes “is this a network note?” a straightforward, first-class operation.

• Centralizes the parsing/validation logic instead of spreading it across call sites.

• Enables extracting additional network-note-specific properties, e.g.:

  • target account ID

Acceptance Criteria

• NetworkNote::try_from(Note) (or &Note) returns:

  • Ok(NetworkNote) if the note is a network note
  • an error otherwise (ideally informative enough to debug misuse)

• NetworkNote exposes helper accessors for common fields (at minimum: target account ID)

Why is this feature needed?

DevEx

[bobbinth]

This may be as simple as copying NetworkNote enum from miden-node into miden-standards.