chore(upgrade-coverage): add no-op 0.12-to-0.13 extension-author entry

This PR's `packages/3-extensions/` diff is the internal sql-orm-client
include-codegen refactor (none of the touched symbols —
`selectIncludeStrategy`, `compileSelectWithIncludeStrategy`,
`buildLateralIncludeArtifacts` — are part of the package's public
`exports/index.ts` surface) plus its tests. Extension authors consuming
`@prisma-next/sql-orm-client` see no API change, so the transition is a
no-op for them: `changes: []`.

Satisfies `pnpm check:upgrade-coverage --mode pr`, which requires an
extension-upgrade directory for the in-flight 0.12 -> 0.13 transition
whenever a PR touches `packages/3-extensions/`. Mirrors the no-op
0.12-to-0.13 entry already shipped for the user-upgrade skill.

Refs: TML-2729
Signed-off-by: Alexey Orlenko's AI Agent <robot@aqrln.net>

Author: tensordreams

skills/extension-author/prisma-next-extension-upgrade/upgrades/0.12-to-0.13/instructions.md

@@ -0,0 +1,5 @@
+---
+from: "0.12"
+to: "0.13"
+changes: []
+---