inspect: add Temporal support

[Renegade334]

Example output:

> Temporal.Now.instant()
Temporal.Instant 2026-05-06T16:19:21.226404053Z

> class XYZ extends Temporal.Duration {}
> new XYZ(1, 2, 3, 4, 5, 6, 7, 8, 9)
XYZ [Temporal.Duration] P1Y2M3W4DT5H6M7.008009S

> Object.assign(Temporal.Now.zonedDateTimeISO('Pacific/Honolulu'), { foo: 'bar' })
Temporal.ZonedDateTime 2026-05-06T06:24:22.920191895-10:00[Pacific/Honolulu] {
  foo: 'bar'
}

The Temporal global obviously has to be lazily accessed, and there's no way to do it that's immune from potential user tampering. The approach taken here is just to fetch it from the global object every time, since the output of inspect() is inherently aimed at the human reader, so it doesn't really need to be particularly hardened.

WIP: tests

[ljharb]

i'm confused, why would it need to be lazily accessed instead of using primordials?

[ljharb]

Temporal itself exposes type checks via internal slots and builtin methods.

[Renegade334]

Yes, but we can't guarantee a non-mutable path to get our hands on those methods.

[ljharb]

of course we can, via primordials

[Renegade334]

Not while Temporal remains an optional feature, unfortunately.

[ljharb]

it's not? node 26 ships it unconditionally.

[Renegade334]

It's enabled by default, but remains behind both runtime (cf. --no-harmony-temporal) and build flags, so this is unlikely to change any time soon.

[ljharb]

ahhh gotcha. surely we can still capture the builtins at startup, though, even if they're not real primordials yet?

[Renegade334]

It's too early. Attempting to capture the global with something like const { Temporal } = globalThis in the header of inspect.js always hits thin air (I guess it's snapshotted?). We have to do it lazily from inspect(), at which point anything that intends to modify the Temporal global (polyfills etc.) will almost certainly already have run.

We could go full ham to hack around this, but it's not really a huge issue in the context of a function which only uses those methods to decide what flavour of human-readable output gets generated.