[WIP] Fix CI failures in PR #974 due to Scala 2 errors

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Implementation Plan: Fix PR zio#974 CI failures

Problem and approach

• CI fails in PR Schema migration system for ZIO Schema 2 zio/zio-blocks#974 due to Scala 2 compilation errors in MigrationBuilderSyntax.scala and branch coverage below minimum for schema migrations (~78-79% vs 80%).
• Fix Scala 2 macro syntax/regressions first, then add/extend migration tests to raise coverage.
• Re-run targeted sbt tests/coverage locally; note CLA check is external.

Workplan

• Fetch and check out the PR branch with: git fetch origin pull/974/head:pr-974 && git checkout pr-974.
• Inspect Scala 2 macro file: schema\shared\src\main\scala-2\zio\blocks\schema\migration\MigrationBuilderSyntax.scala (focus around macro defs for addField/rename/etc. lines ~70-140).
• Compare to Scala 3 version for intent: schema\shared\src\main\scala-3\zio\blocks\schema\migration\MigrationBuilderSyntax.scala.
• Fix Scala 2 macro definitions so schemaJVM/schemaJS compile under 2.13; likely syntax regression in macro defs.
• Fast compile check (Scala 2.13): sbt ++2.13.x schemaJVM/compile then schemaJS/compile to confirm macro fix.
• Run Scala 2.13 tests: sbt ++2.13.x schemaJVM/test and sbt ++2.13.x schemaJS/test.
• Generate schema coverage for Scala 3.3.x: sbt ++3.3.x coverage schemaJVM/test coverageReport.
• Locate uncovered migration branches from scoverage HTML in schema/.jvm/target/scala-3.3.x/scoverage-report/index.html, then add/extend tests in schema\shared\src\test\scala\zio\blocks\schema\migration\*.
• Re-run Scala 3 coverage to confirm branch coverage >= 80%.
• CI-aligned smoke tests: sbt ++2.13.x schemaJVM/test and sbt ++3.3.x schemaJVM/test (plus schemaJS/test if touched JS paths).

Notes / considerations

• The CLA check is pending and must be signed by the PR author; it cannot be fixed in code.
• Keep changes minimal and focused on migration syntax and coverage.
• Executor should minimize file reads: open only the two MigrationBuilderSyntax.scala files and the specific migration test files being edited.

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