refactor: remove supercharge/god-tier/singularity references from all source files

Replace informal hype labels with neutral technical language: - store.py: "supercharge plan" → "architecture phase" - diff_algorithms/__init__.py: "supercharge plan" → "domain schema architecture" - _crdt_notes.py: "supercharge plan" → "live collaboration architecture" - Rename docs/architecture/supercharge-plan.md → architecture-plan.md and update the document title to match