Writing a Timestamp in the last ~26h of year 9999 panics during Min/Max stats #8860

What happens

When a Timestamp column holds a value greater than jiff's Timestamp maximum (253402207200 s = 9999-12-30T22:00:00Z), VortexWriteOptions::write panics (via vortex_panic!) while computing the Min/Max statistic. Vortex builds an extension Scalar for the min/max value and validates it through jiff; for values in the last ~26 hours of year 9999 that validation fails and surfaces as a panic rather than an error. Arrow, Parquet, and many SQL engines allow timestamps up to 9999-12-31T23:59:59, so this can be triggered by ordinary in-range data.

Version: vortex 0.78.0.

Minimal repro (only depends on vortex = "=0.78.0"):

use std::sync::LazyLock;
use vortex::VortexSessionDefault;
use vortex::array::arrays::{ExtensionArray, StructArray};
use vortex::array::extension::datetime::{TimeUnit, Timestamp};
use vortex::array::{ArrayRef, IntoArray};
use vortex::buffer::{ByteBufferMut, buffer};
use vortex::dtype::Nullability;
use vortex::file::WriteOptionsSessionExt;
use vortex::io::runtime::BlockingRuntime;
use vortex::io::runtime::current::CurrentThreadRuntime;
use vortex::io::session::RuntimeSessionExt;
use vortex::session::VortexSession;

static RUNTIME: LazyLock<CurrentThreadRuntime> = LazyLock::new(CurrentThreadRuntime::new);
static SESSION: LazyLock<VortexSession> =
    LazyLock::new(|| VortexSession::default().with_handle(RUNTIME.handle()));

fn write_one_timestamp(ts_micros: i64) -> usize {
    let ext = Timestamp::new(TimeUnit::Microseconds, Nullability::NonNullable).erased();
    let storage: ArrayRef = buffer![ts_micros].into_array();
    let ts: ArrayRef = ExtensionArray::new(ext, storage).into_array();
    let table = StructArray::from_fields(&[("t", ts)]).unwrap().into_array();
    let mut buf = ByteBufferMut::empty();
    RUNTIME.block_on(async { SESSION.write_options().write(&mut buf, table.to_array_stream()).await })
        .expect("write should succeed");
    buf.len()
}

fn main() {
    const IN_RANGE:   i64 = 253_402_207_200_000_000; // 9999-12-30T22:00:00Z (jiff max) — OK
    const OVER_RANGE: i64 = 253_402_214_400_000_000; // 9999-12-31T00:00:00Z — panics
    println!("in-range: wrote {} bytes", write_one_timestamp(IN_RANGE));
    println!("over-range: wrote {} bytes", write_one_timestamp(OVER_RANGE)); // panics here
}

Output:

in-range  (9999-12-30 22:00:00Z): wrote 2676 bytes
over-range (9999-12-31 00:00:00Z): writing...
thread 'main' panicked at vortex-error-0.78.0/src/lib.rs:347:
unable to construct an extension `Scalar`:
  Other error: Invalid timestamp scalar: parameter 'Unix timestamp seconds' is not in the required range of -377705023201..=253402207200

The value at the limit (9999-12-30T22:00:00Z) writes fine; the same column two hours later aborts, which points to the jiff range boundary.

Root cause

• aggregate_fn/fns/min_max/extension.rs::accumulate_extension computes min/max on the i64 storage, then wraps the results with the infallible Scalar::extension_ref (internally Scalar::try_new(...).vortex_expect("unable to construct an extension Scalar")).
• extension/datetime/timestamp.rs::unpack_native validates via jiff::Timestamp::UNIX_EPOCH.checked_add(span), and jiff intentionally reserves headroom (so a Timestamp stays convertible to a civil datetime in any timezone), so it can't represent the final ~26h of year 9999.
• The fallible result becomes a panic, which aborts the writer — in our case across a C FFI boundary, so it takes down the whole process.

Expected behavior

Ideally, support the full timestamp range that Arrow and Parquet allow (through the end of 9999-12-31). Alternatively, skip the Min/Max statistic when a value can't be represented as an extension scalar — the data itself round-trips fine, so dropping the stat for that column/chunk is preferable to a panic.