Release FiveFury 0.5.1 with shared META I/O optimizations

[Hancapo]

YMAP reads now construct typed entities and extensions through schema-checked native bindings, and the shared META writer encodes graphs in C++ while retaining generic handling for unknown layouts and custom extension registrations. Root blocks stay separate from child blocks of the same type, fixing a metadata overwrite during graph construction.

Prepare FiveFury 0.5.1 with the accumulated animation and resource I/O improvements documented in the changelog. The README now presents the library for research and education, with installation, two runnable examples and a concise scope table. The local .NET port is excluded from Git and source distributions.

Validation:

• Built wheel and sdist; metadata reports version 0.5.1 and neither archive contains .NET files.
• Installed-wheel unit and ABI checks: 2,129 passed, including the Python 3.11 ABI floor; 7 subtests passed.
• Ruff and package metadata checks passed.
• Independent review completed for the META/model implementation; five canonical YMAP rewrites preserved their bytes.
• Full Python 3.11–3.14 release matrix passed on commit a2acfdc: https://github.com/Hancapo/fivefury/actions/runs/34720989116.
• All 52 performance API cases passed with timing disabled; obsolete block-grouping cases now use the public builder.
• Both README examples executed successfully, and both distributions contain the exact revised README and summary.