[BLCCoreStudio]

Summary

Adds an eighth curated comparison: Git vs Apache Subversion.

The comparison focuses on architectural choices rather than treating distributed version control as universally superior to centralized version control.

Compared dimensions

• repository authority
• history model
• revision identity
• local working-state model
• commit path
• offline history and commits
• branch model
• tag model
• merge tracking
• history rewriting
• authorization granularity
• sparse/partial access
• binary locking
• versioned metadata
• server dependency
• backup/recovery
• large centralized tree behavior
• CI/release identity
• migration boundaries
• strong-fit conditions
• explicit non-equivalence boundaries

Decision guidance

• local commits/history/branches while offline -> Git
• subtree-level centralized authorization -> Subversion
• huge centralized trees with selective checkout -> Subversion
• Git-hosting/DAG/topic-branch workflows -> Git
• lock-oriented binary workflows -> Subversion
• migration decisions based on repository architecture and operating requirements rather than age/popularity

Discovery and module integrity

• adds tool/subversion to the catalog so the comparison builder does not reference an unknown module
• adds a real tool/subversion module branch with schema-aligned metadata and an overview page, so generated comparison links resolve to actual module content
• keeps Subversion at overview maturity for now; this PR does not claim deep-dive coverage until the module has been independently expanded and reviewed

The generic comparison validator derives graph membership and backlinks automatically. Coverage changes should be reported from generated metrics rather than hard-coded in this PR description.