feat: Add RAII-mode macro for memory management (minimal changes)

[scc-tw]

Background

This project currently uses reference counting for memory management, primarily for CPython compatibility. To enable more aggressive memory compaction, we want to introduce a new macro to switch to RAII-mode memory management when desired.

Requirements

• RAII Mode Activation:
  • Only enabled when -DRAII_MODE=ON is set via CMake option.
• Macro Implementation:
  • Add a new macro to enable RAII-based memory management.
  • Use macro guards, but minimize their usage scope to only where necessary.
• Code Quality:
  • Write clean, expert-level C++ code.
  • Minimal code changes: Only modify/refactor code directly impacted by the new macro.
• Documentation Review:
  • Read all documentation in the docs/ folder to fully understand existing design and constraints before implementation. See the references below for a complete list of documents.
• Compatibility:
  • When RAII is not enabled, retain the current reference counting approach for CPython compatibility.
• Goal:
  • Allow move-aggressive memory compaction when RAII is available, with minimal disruption to current functionality.

Acceptance Criteria

• New macro is added and properly guarded.
• CMake option -DRAII_MODE=ON switches the project to RAII mode.
• Only minimal code changes are made to enable RAII.
• Code quality meets expert C++ developer standards.
• Documentation is reviewed prior to implementation.

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References:

• docs/content/index.md
• docs/content/Architecture/Building.md
• docs/content/Architecture/Handle.md
• docs/content/Architecture/Tests.md
• docs/content/Architecture/Types.md
• docs/mkdocs.yml