tests/functional.lsp — single .lsp file, runs identically in Python and C.
Covers: arithmetic, comparison, booleans, pairs, lists, strings, characters,
vectors, hash tables, control flow, let/lambda/closures, do loops, define,
recursion, TCO (100k depth), quasiquote, macros, type predicates, call/cc,
error handling, mergesort, higher-order programs.
Fixed C call/cc: proper escape continuations via setjmp/longjmp.
make test-all runs: Python unit (571) + C unit (58) + shared functional (114).