Add Eclipse release compatibility matrix CI with parameterized Tycho target selection

[Copilot]

This PR introduces an Eclipse-version compatibility check that builds the plugin against release targets from 2024-06 through 2026-03. It also parameterizes target resolution in Maven so the same source can be validated across multiple Eclipse target platforms without editing project files.

• Compatibility workflow

  • Adds .github/workflows/compatibility.yml with a Windows matrix for:
    • 2024-06, 2024-09, 2024-12, 2025-03, 2025-06, 2025-09, 2025-12, 2026-03
  • Uses quoted Maven -D arguments for PowerShell-safe argument passing.
  • Sets EE constraint resolution per target (true for 2024-*, false for 2025-03+).

• Versioned target platform definitions

  • Adds targets/*.target files for each matrix version, all with the same IU set (org.eclipse.platform.feature.group, org.eclipse.jdt.feature.group) and only release URL varying by version.

• Baseline target indirection

  • Updates target-platform.target to include targets/2024-06.target via type="Target" URI, keeping baseline content centralized in targets/.

• Tycho/Maven parameterization

  • Updates pom.xml to add:
    • target.platform.file (default: target-platform.target)
    • target.resolve.with.ee.constraints (default: true)
  • Wires these into target-platform-configuration:
    • <file>../../${target.platform.file}</file>
    • <resolveWithExecutionEnvironmentConstraints>${target.resolve.with.ee.constraints}</resolveWithExecutionEnvironmentConstraints>

Example workflow invocation pattern:

run: mvn -B clean verify -ntp \
  "-Dtarget.platform.file=targets/${{ matrix.target }}.target" \
  "-Dtarget.resolve.with.ee.constraints=${{ startsWith(matrix.target, '2024-') && 'true' || 'false' }}"