Release 10.4.0: date the changelogs, tag v10.4.0, carry the sections to main #519

Change

These are the release steps now that every in-scope PR of #472 has merged into release/10.x, as #470 did for 10.3.0. Version is already 10.4.0 (#473). The last merges were #518 (#517) and #516 (#512) on 2026-10-26, so the release commit to check is release/10.x at 07d92df or later.

1. Check before the tag. All of the following must hold on the release commit, with every fix merged, so the fixes are checked together rather than one PR at a time:
   • Every CI lane is green: PostgreSQL 16 and 18, on the EF Core floor and on the newest-patch legs (now EF Core 10.0.14), plus both smoke-test modes.
   • dotnet run tools/oracles.cs seeds re-proves locally that every seed is caught (AGENTS.md, workflow step 4).
   • The pre-release reviews already ran, and their findings are fixed (Text set ==, != and Count through a scalar subquery skip #485's rewrite and compare the unsorted array_cat #505, YearMonthRange Clamp and UpperBound() in a filter compare as the month's last day, so == against the month is false #506, A case-insensitive collation on the element side still makes string set Contains and Remove compare case-insensitively #507 and their ports 10.x: follow a text set operation through a scalar subquery in the guard's rewrite (port of #505) #510–10.x: reject a string set compared with a value under a collation that may not compare bytes (port of #507) #512).
2. Date the five changelogs. Set ## [10.4.0] — yyyy-mm-dd in all five, in the commit that gets tagged.
3. Tag v10.4.0 (annotated, like v10.3.0) on that commit. The release workflow publishes the packages, and the nuget environment approval is the maintainer's.
4. Check that no 10.x-only issue is left open. Closes #n acts only on main. Every sub-issue of Epic: 10.4.0 #472 is closed already, so this step only re-checks.
5. Carry 10.4.0 to main in one PR, as chore: carry the 10.3.0 sections to main (#470) #474 did for 10.3.0. It can't build until 10.4.0 is on nuget.org, because the baseline bump restores it.
   • Copy the [10.4.0] sections into main's five changelogs, verbatim.
   • Add ## Changed answers in 10.4.0 to main's docs/migration.md. The 10.4.0 changelog links #changed-answers-in-1040, and the section must cover 10.x: reject a collation on a string set column unless it compares bytes (port of #483) #496, 10.x: read an exclusive infinite date bound as memory loads it (port of #489) #502, 10.x: read a YearMonthRange upper bound in a query as the first day of its month (port of #506) #511 and 10.x: reject a string set compared with a value under a collation that may not compare bytes (port of #507) #512 (on main: Text value set operators follow a nondeterministic column collation: on a case-insensitive column, Contains("a") is true for {A} and Remove("a") deletes A #483, LowerBound(), UpperBound() and Clamp in a query read a date range another tool wrote with an exclusive infinite bound one day wider than memory loads it #489, YearMonthRange Clamp and UpperBound() in a filter compare as the month's last day, so == against the month is false #506, A case-insensitive collation on the element side still makes string set Contains and Remove compare case-insensitively #507).
   • Make whatever changes the conventions then require on main: PackageValidationBaselineVersion, main's SECURITY.md row and the walkthrough sample's package version.
6. Open 10.5.0 on release/10.x, as Open 10.4.0 on release/10.x #473 did after 10.3.0: Version, the baseline, the SECURITY.md row and the sample move on. Translate ToRangeSet() from Int32Set, Int64Set, DateSet, LocalDateSet and YearMonthSet (split from #407) #487 is already deferred to 10.5.0.

Done when

• v10.4.0 is on nuget.org for all four packages.
• GitHub's Latest release is still the highest stable version.
• Epic: 10.4.0 #472 is closed with a summary.
• main carries the 10.4.0 sections.