Generalize ExpertMesh project identity

[manishklach]

What changed

• Renamed the public-facing project identity from ExpertMesh K3 to ExpertMesh.
• Changed the Python distribution name to expertmesh-fabric while retaining the expertmesh import package.
• Updated README badges, documentation, roadmap, changelog, SVG title, and editable FigJam diagram.
• Retained Kimi K3 only as an explicitly labeled example sizing profile for the generic planner.

Why

The stationary-expert architecture and HIP/runtime work apply to configurable sparse MoE checkpoints, not one specific model family.

Validation

• pytest -q — 6 passed
• ruff check src tests — passed
• pip wheel . --no-deps — built expertmesh_fabric-0.1.0
• SVG XML validation — passed
• git diff --check — passed