scripts/check-inputs.mjs declares every Validate check with its roots and
entry points and computes the rest: imports and path literals of the
entries, transitively for code, as leaves for data. classify-changes and
gate-reuse both read it, so "which job runs" and "what its key hashes"
cannot disagree any more. An executable file no check knows widens the run
to the full set and is named in the summary; the coverage list makes such
a file a red unit test rather than a permanent widening. The workflow file
is a toolchain input of every job; backend no longer hashes src/**.
Issue: #492
User-Visible: no
