Add Eclipse release compatibility matrix CI with parameterized Tycho target platform resolution

[Copilot]

This PR adds a compatibility workflow to compile the plugin against Eclipse releases 2024-06 through 2026-03 without source edits per target. It also parameterizes Tycho target-platform resolution so CI can switch target files and EE-constraint behavior by matrix entry.

• CI: Eclipse compatibility matrix

  • Added .github/workflows/compatibility.yml with a Windows matrix over:
    • 2024-06, 2024-09, 2024-12, 2025-03, 2025-06, 2025-09, 2025-12, 2026-03
  • Maven invocation is property-driven and quoted (PowerShell-safe):
    • -Dtarget.platform.file=targets/<version>.target
    • -Dtarget.resolve.with.ee.constraints=<true|false>
  • EE constraints are enabled for 2024-* and disabled for 2025-03+ to allow resolution of JavaSE-21 IUs during compatibility checks.

• Build config: Tycho target parameterization

  • Updated root pom.xml:
    • Added target.platform.file (default: target-platform.target)
    • Added target.resolve.with.ee.constraints (default: true)
    • Wired both into target-platform-configuration:
      • <file>../../${target.platform.file}</file>
      • <resolveWithExecutionEnvironmentConstraints>...</resolveWithExecutionEnvironmentConstraints>

• Target platform definitions

  • Added targets/ with 8 versioned target files:
    • 2024-06.target, 2024-09.target, 2024-12.target, 2025-03.target, 2025-06.target, 2025-09.target, 2025-12.target, 2026-03.target
  • Each target points to https://mirrors.aliyun.com/eclipse/releases/<version>/ and keeps dependency units aligned with current project target usage.

• Baseline target indirection

  • Updated target-platform.target to reference targets/2024-06.target via type="Target" so baseline contents live in one canonical target file.

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