feat(test): show sub-millisecond test durations

[lunadogbot]

Problem

Test durations under 1ms were truncated to 0ms in the test reporter output, because the elapsed time was converted with duration.as_millis() as u64 before reaching the reporters. This made fast tests look like they took no time at all:

OrderStatusHistoryMapper → toDto should map entity to DTO ... ok (1ms)
OrderStatusHistoryMapper → toDtoArray should map multiple entities to an array ... ok (0ms)

Closes #30785

Changes

Following the maintainer's guidance in the issue, the full Duration is now threaded through the test pipeline instead of being pre-truncated to milliseconds:

• TestEvent::Result, Slow, and StepResult now carry a Duration instead of u64 milliseconds.
• The reporter trait (and all reporters: pretty, dot, tap, junit, compound, plus the LSP test reporter) now take a Duration.
• display::human_elapsed now accepts a Duration and renders sub-millisecond durations in microseconds (µs) or nanoseconds (ns), matching the units already used by the deno bench reporter. Output for durations ≥ 1ms is unchanged.
• The JUnit reporter now records more precise timings as well (it previously rounded to whole milliseconds).

After the change:

fast sync test ... ok (18ms)
tiny map test ... ok (278µs)
noop ... ok (145µs)

Notes

• Test steps still report at millisecond resolution because they are timed in JS via Date.now(). That was left out of scope to keep this change focused on the top-level test durations the issue is about; the millisecond value is converted to a Duration at the op boundary so there's no behavior change there.
• Existing spec tests match the timing field with ([WILDCARD]), so they remain compatible.

Tests

• Added test_human_elapsed_sub_millisecond covering the ns/µs/ms boundaries, and updated test_human_elapsed for the new signature.

https://claude.ai/code/session_012SJDri5NiiSbGVrYq6hsNQ

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