Subsecond console flush intervals are rounded down

### Feature Summary

`TimedBuffer` measures elapsed time with the whole-seconds `timedelta.seconds` field but compares it to a millisecond configuration. Subsecond thresholds are rounded down, so the default 500 ms console flush does not occur until at least one full second has elapsed.

Expected behavior: messages flush as soon as the configured millisecond interval is reached.

Before: a 500 ms buffer still holds a message after 600 ms

After: the message flushes at the 500 ms boundary

Reproduction evidence:

Create a `TimedBuffer` with a 500 ms interval, add one message, set its last output time 600 ms in the past, and call `get`. The returned iterator is empty.

Version and commit evidence:

1.3.0-incubating-SNAPSHOT on main

**Commit Hash (Optional)**
50321e403c82df299a13deb50a7f9849dd93bdba

**Browsers**

Not browser specific

**Relevant log output**

At 600 ms elapsed, zero messages are emitted and one remains buffered.

### Proposed Solution or Design

Expected behavior: messages flush as soon as the configured millisecond interval is reached.

After: the message flushes at the 500 ms boundary

### Affected Area

Workflow Engine (Amber)