docs: Demo animation and update to README formatting

[toby-coleman]

Summary

Adds an animation demo to the README and updates formatting.

Changes

• Demo is located in docs/assets and requires vhs to generate the GIF animation.

[github-actions]

Benchmark comparison for 78e8f549 (base) vs df811df8 (PR)

------------------------------------------------------------------------------------------------------------------ benchmark: 2 tests -----------------------------------------------------------------------------------------------------------------
Name (time in ms)                                                                         Min                 Max                Mean            StdDev              Median               IQR            Outliers     OPS            Rounds  Iterations
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
test_benchmark_process_run (main/.benchmarks/Linux-CPython-3.14-64bit/0001_base)     536.9293 (1.0)      546.9564 (1.01)     542.6322 (1.00)     3.8448 (4.64)     541.9959 (1.00)     4.9880 (3.33)          2;0  1.8429 (1.00)          5           1
test_benchmark_process_run (pr/.benchmarks/Linux-CPython-3.14-64bit/0001_pr)         540.8358 (1.01)     542.7415 (1.0)      541.8232 (1.0)      0.8294 (1.0)      541.8260 (1.0)      1.4998 (1.0)           2;0  1.8456 (1.0)           5           1
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Legend:
  Outliers: 1 Standard Deviation from Mean; 1.5 IQR (InterQuartile Range) from 1st Quartile and 3rd Quartile.
  OPS: Operations Per Second, computed as 1 / Mean

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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