The member scan's known-truncated roster names the buffer drill-down's nullable rounder (#3691 lane 29 residue; dev red since #3795)

[erikdarlingdata]

What does this PR do?

Dev has been red on TsqlConventionGuardTests.TheMemberScan_ReadsEveryDeclarationWhole since #3795 (lane 29 of #3691): the buffer-composition drill-down added a nullable four-place rounder, PgTargetDrillDownCollector.Buffer.cs Round, whose declaration range the member scan reads short — the same expression-shaped helper as the Figure / Count / Tally formatter lines already on the roster. What its range strands is Math.Round(value.Value, 4) and nothing else: no T-SQL, no tempdb label, no SQL literal any census reads, so the scan stopping short of it loses no counted site. The test itself says "edit KnownTruncatedRanges to match and say which in the PR body": the direction is ARRIVED, one line, with the reason beside it.

One file, test roster only; no product change. #3799 (the drill-down's other census fix) did not cover this one.

Which component(s) does this affect?

• Darling Tests

How was this tested?

Darling.Tests builds (-p:EnableWindowsTargeting=true, 0 warnings / 0 errors); the class executes in CI's build and Darling PostgreSQL tests jobs, which listed exactly this one member. CRLF preserved (verified byte-wise).

Checklist

• I have read the contributing guide
• My code builds with zero warnings of its own
• No hardcoded credentials or server names