SDKMan ANSI color codes pollute JAVA_HOME during network issues

Description

During GitHub's infrastructure outage on Feb 9-10, 2026, a merge queue run failed because SDKMan's colored error output was captured as the JAVA_HOME environment variable value, causing GitHub Actions to reject it with 'Invalid format'.

Failed Run: https://github.com/dotCMS/core/actions/runs/21876576401

Root Cause: When SDKMan encountered network connectivity issues (due to GitHub's outage), it printed a colored 'INTERNET NOT REACHABLE' warning message with ANSI color codes ([1;31m, [0m). These codes were captured in the JAVA_HOME variable and written to $GITHUB_ENV, which GitHub Actions rejected.

Context: This was triggered by GitHub's infrastructure outage affecting runner network connectivity. First observed occurrence, likely to recur during network issues. Impact: Blocks merge queue runs (false positive - Java was actually configured correctly).

Acceptance Criteria

• Add SDKMAN_COLOUR_ENABLE=false to setup-java action before sourcing sdkman-init.sh
• Add SDKMAN_AUTO_ANSWER=true to prevent interactive prompts
• Add SDKMAN_AUTO_SELFUPDATE=false to disable auto-updates in CI
• Test that JAVA_HOME is set correctly without ANSI codes during simulated network issues
• Document the change in workflow documentation

Alternative: This issue may become obsolete if we migrate from SDKMan to mise for SDK management, which is faster, more CI-friendly, and better suited for modern DevOps workflows.

Priority

Low - This was triggered by a transient GitHub outage (now resolved). The fix is simple but may not be needed if we migrate to mise.

Additional Context

Proposed Fix Location: .github/actions/core-cicd/setup-java/action.yml (before line 101)

# Disable SDKMan color codes in CI to prevent environment variable pollution
export SDKMAN_COLOUR_ENABLE=false
export SDKMAN_AUTO_ANSWER=true
export SDKMAN_AUTO_SELFUPDATE=false

References:

• Diagnostic Report: .claude/diagnostics/run-21876576401/DIAGNOSIS.md
• GitHub Outage: Feb 9-10, 2026 'Incident with Issues, Actions and Git Operations'
• Related: GitHub Community Discussion #137976 (merge queue orphaned workflows)

Start with .github/actions/core-cicd/setup-java/action.yml around line 101 and review .claude/diagnostics/run-21876576401/DIAGNOSIS.md alongside the failed Actions run. Verify the SDKMan settings prevent ANSI text from entering JAVA_HOME during simulated network failure, then confirm the workflow documentation records the change.