Xqlite.TypeExtension.Instant (Xqlite v0.8.0)

Encode-only type extension: DateTime → int64 nanoseconds since the Unix epoch.

The integer-instant alternative to Xqlite.TypeExtension.DateTime's ISO 8601 text. Both claim DateTime structs, so pick ONE per chain — or rely on first-match ordering, where whichever extension is listed first wins the struct.

There is deliberately no decode: a nanosecond instant is indistinguishable from any other stored integer. Read-side conversion belongs to the caller (or to the Ecto layer's XqliteEcto3.Types.Instant, which this module mirrors).