[CaffeinatedCoder]

Closes #470

Problem

This is step 5 of #470, after v10.3.0 shipped: the tag is on 2230e73, all four packages are on nuget.org, and the GitHub release is Latest. main keeps the sections of every release on both lines, but it has no 10.3.0 changelog sections yet. The v10.3.0 notes link to blob/main/docs/migration.md#changed-answers-in-1030, which doesn't exist on main.

Change

• Five changelogs: each ## [10.3.0] — 2026-10-25 section, copied verbatim from v10.3.0, between 11.0.0-preview.1 and 10.2.0.
• docs/migration.md: a short ## Changed answers in 10.3.0 section that links the two subsections already under ## Migration from v10.x, as chore: carry the 10.2.0 sections to main (#365) #413 did for 10.2.0. Their 10.x text differs from main's only in "Before 10.3.0" versus "Before 11.0.0". The subsections now say "Before 10.3.0", when the change shipped. The v10.x intro says the last two items of its list also shipped in 10.3.0.
• Directory.Build.props: PackageValidationBaselineVersion moves from 10.2.0 to 10.3.0.
• SECURITY.md: the rows become 10.3.x ✅ and < 10.3 ❌.
• samples/Bookings/Bookings.csproj: the package version moves to 10.3.0, along with the baseline.

Tests

• The conventions suite passes, 417 of 417, on SDK 11.0.100-rc.2, after restoring the 10.3.0 baseline from nuget.org (--no-http-cache).
• dotnet pack -c Release validates all four packages against the 10.3.0 baseline without errors.
• Every anchor that the new migration section links exists on this branch.

🤖 Generated with Claude Code