Keep fractional Slack timestamps in bounded thread reads

When a Slack thread-read connector documents fractional timestamp strings, preserve the decimal component when converting a UTC cutoff. A whole-second string can produce a successful parent-only response, making existing replies look absent. Before treating an empty bounded read as evidence, retry with the documented timestamp shape and compare a fully paginated thread read filtered locally. This observation concerns one connector; it does not establish identical behavior across Slack APIs or prove a server defect.

Applies when: An audit limits Slack thread replies to a fixed cutoff. Keywords: Slack timestamp fractional decimal cutoff thread replies empty pagination