Format precise durations without calendar date limits

[xiehuanyi]

precisedelta(timedelta(days=4_000_000)) currently raises OverflowError: date value out of range. The duration itself is valid; the failure comes from constructing a calendar date that this formatter never uses. The same limit affects numeric seconds and timedelta.min/timedelta.max.

Operate directly on absolute timedeltas for duration inputs, retaining the existing relative-date path for datetime inputs. Annotate the unit accumulators as float because unit suppression and minimum-unit rounding can produce fractional counts.

Six regressions cover signed4-million-day timedeltas, the corresponding numeric seconds, and the timedelta bounds. All six fail before the fix. Afterward,735 behavior/doctest cases pass with112 translation-related skips, strict mypy . passes, all repository prek hooks pass, and git diff --check passes. Performance benchmarks were excluded from this behavior run.

Prepared with AI assistance.

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