Show and verify the real Cleanup preview

[carstenartur]

Summary

Starts the implementation of #1452 and fixes the first product defects uncovered by the real-preview audit.

• exposes the previously hidden JFace Cleanup master option so the visible child options can drive execution;
• gives the three JFace migrations distinct user-facing Cleanup preview labels;
• returns one step description per enabled JFace migration instead of one generic enum-based description;
• adds regression coverage for the distinct labels.

Next commits in this PR

• deterministic real Source > Clean Up... SWTBot fixture;
• one-file/multiple-step and multiple-file preview interaction tests;
• application and undo assertions;
• canonical preview screenshots and linked Eclipse Help;
• refreshed JFace configuration screenshot after the master-option fix.

The coordinated multi-file candidate atomicity problem remains separated in #1451.

Refs #1452
Refs #1451

[github-actions]

Static source inventory only: this workflow lexically scans Java code while ignoring comments, strings, character literals and text blocks. It does not compile or execute tests. The authoritative build/test signal is Java CI with Maven.

JUnit Test Overview Report

Generated on: 31339683806

Overall Statistics

• Total Test Modules: 16
• Total Test Files: 211
• Total Tests: 1401
• Enabled Tests: 1401 (100.0%)
• Disabled Tests: 0 (0.0%)

Test Summary by Plugin

Plugin	Test Files	Total Tests	Enabled	Disabled	Disabled %
sandbox_cleanup_application_test	4	50	50	0	0.0%
sandbox_common_test	55	376	376	0	0.0%
sandbox_css_cleanup_test	5	43	43	0	0.0%
sandbox_encoding_quickfix_test	5	18	18	0	0.0%
sandbox_functional_converter_test	35	365	365	0	0.0%
sandbox_int_to_enum_test	11	31	31	0	0.0%
sandbox_jface_cleanup_test	3	12	12	0	0.0%
sandbox_junit_cleanup_test	50	281	281	0	0.0%
sandbox_method_reuse_test	1	1	1	0	0.0%
sandbox_platform_helper_test	3	7	7	0	0.0%
sandbox_test_commons	12	29	29	0	0.0%
sandbox_tools_test	1	2	2	0	0.0%
sandbox_triggerpattern_test	15	101	101	0	0.0%
sandbox_usage_view_test	5	20	20	0	0.0%
sandbox_use_general_type_test	1	15	15	0	0.0%
sandbox_xml_cleanup_test	5	50	50	0	0.0%

Disabled Tests Details

No disabled tests found! 🎉

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Generated by the Test Source Inventory workflow

[carstenartur]

Superseded by #1464, which consolidates the real Cleanup preview work with the coordinated-candidate UI and release verification on an owner-controlled branch. Closing this partial implementation to keep one authoritative integration path.