ImportBase opened the input with a default std::fstream (in|out), which had
two consequences: a missing file silently produced an empty module (no error),
and a present-but-read-only file failed to open and also loaded as empty. Open
the stream read-only (std::ios::in) instead, and expose is_open().
System::Load now builds the importer first, checks is_open(), and throws
"cannot open file: <path>" before creating the module — so a failed load
surfaces as `load failed: …` and leaves no empty module behind. A read-only
but present file now loads correctly.
Flip the test that pinned the old silent-empty behaviour to assert the clean
failure (error + no module created).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Move the import orchestration — System::Load + drop_singleton_signals +
infer_signal_types + the post-import counts — out of the `load` command into
core/app/load.{hpp,cpp}: app::load_module(System*, name, path, ImportType)
returns a LoadResult (ok/error, parts, signals, dropped, power/gnd/kept_other)
with no Print/dialog/FTXUI. The "mentor|altium|ods" string→enum mapping moves
to app::import_type_from_name (mirrors export_format_from_path). The command
only parses the type and renders the counts; output is byte-identical.
Add tests/test_load.cpp (core, no UI): the name mapping; a minimal Mentor
netlist that imports two parts and drops one singleton signal; and a pin test
of the pre-existing missing-file behaviour (ImportBase doesn't check is_open(),
so a missing file yields an empty module rather than an error — preserved by
the extraction and pinned so any future hardening is a deliberate change).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
