Count by module directory (51) throughout, and state the directory-vs-script-
class discrepancy up front: filesystem also exposes HotReload, Cmdline lives in
engine/cmdline, and data/tensor bind under different class names.
Also align the layer diagram with the script's computed depths, add math and
audio to the functional-domain table, and correct the figures that were
estimated during drafting (97 soft lookups, 202 cross-module includes,
136 Poco include sites of which 79 are JSON).
Co-authored-by: 西风逍遥游 <sunxfancy@gmail.com>
