Replace the v1 minimal preamble in the generated ./configure with the
full argument-parsing section (src/gen/args.{h,c}): -h/--help usage,
--version, --prefix/--exec-prefix/--host/--build in = and space forms,
per-DSL-option --enable-<name>/--disable-<name> (default from the
option's default property), generic positional VAR=VALUE overrides
(identifier-validated, single-quote-escaped eval assignment), unknown
--* -> usage on stderr + exit 1, cross_compiling=yes when --host differs
from --build. The substitution set gains exec_prefix/host/build/
cross_compiling plus one enable_<name> per option. Option names are
validated as shell identifiers at generation time.
Tests: 12 new /gen/args/* cases (help lists --prefix/--enable-debug/
--disable-debug; CC=clang positional + env; enable/debug default;
cross_compiling observable; --bogus/--bogus=1/--enable- errors;
--prefix missing/empty; space form; exec_prefix defaulting; VAR=VALUE
injection inert; hostile option name errors at generation) - 28/28
green, three-shell -n + banned-construct sweep clean.
Extension discovery (plan todo 20): scans --ext-dir dirs,
STUPIDTOOLS_EXT, the XDG user dir and a builtin-ext dir for *.lua
modules, runs each in the sandboxed Lua runtime, and enumerates its
registrations; the builtin C/C++ modules load first via
st_ext_init_builtins. Fail-fast with an error naming file and line on
any malformed/sandbox-violating module.
The CLI gains a repeatable --ext-dir flag; with flag or env present
main.c runs discovery and prints 'loaded extension: ...' lines from
actual registrations (interim wiring until todo 23).
Note: src/Makefile.am gained the ext + vendored Lua sources because
the binary otherwise cannot link discovery -- required for the
root-verifiable CLI acceptance.
huntedbytheirs