Normalize timestamp precision before bounded source reads

When an external collection API expects timestamps at a fixed precision, serialize query bounds to that precision before asking it for a history window. A higher-precision floating-point string may be accepted as a valid request yet return an empty successful page, so retries with unchanged malformed bounds can never repair coverage. Keep the prior-observation anomaly guard as a separate defense, and verify the bound format with the same API from the production runtime. This extends the earlier lesson: backoff helps transient omissions, whereas a deterministic query-format fault needs a corrected query.

Applies when: A bounded API read unexpectedly omits previously observed items. Keywords: timestamp precision fractional seconds history query empty success coverage