CLI regression suite

[HanifKoh]

Replaces the single run_test.py script with a pytest-based black-box suite for the orca-slicer CLI. run_test.py is kept as the compatibility entry point OrcaSlicer's own CI already calls (build_orca.yml, "Run external slicer regression tests"), so that integration keeps working unchanged: it sets up a venv on first run and delegates to pytest.

What the suite covers

• Declarative regression cases (cases/**/*.yaml, 63 cases): crash resistance under crafted arguments, CLI parsing, config precedence, bed/array bounds, settings import, CLI action/transform flags, custom G-code emission, per-object overrides. Each case is CLI args plus checks; status: open cases are strict xfails, so an upstream fix flips them loudly instead of drifting.
• Golden slices: every test_projects/*.3mf must slice; metrics (layers, max Z, filament, E sum, time, size) are compared to baseline.json and drift is reported, not failed.
• Config-surface fuzzing: the ~890 accepted options enumerated from PrintConfig.cpp, poisoned per type, daily-rotating sample by default and --fuzz-full for a sweep.
• Settings import/export matrix: presets, filaments, overrides and --uptodate through every export path, with the three artifacts cross-checked.
• Override sweep: every config option set on the command line must land in the merged config and in the sliced G-code's config block.

TESTING_STRATEGY.md documents each layer, the case schema and the status model.

Reference build

Case statuses describe OrcaSlicer main, the build OrcaSlicer's CI runs the suite against. This repo's own workflow self-checks the suite against the nightly AppImage published from main (through AppRun, with the matching source tree cloned for the option surface); a release tag can be tested on demand via the orca_ref dispatch input.

Verification

Against main 37e1582c4c (local Release build): 99 passed, 3 skipped, 9 xfailed in 2 m 17 s. The full nil fuzz sweep over all 243 vector options passes. The suite also ran cleanly through the nightly AppImage's AppRun. OrcaSlicer/OrcaSlicer#15453 runs this branch inside OrcaSlicer's own CI.

The nine still-open cases on main: load-defaultfila, cli-config-repair-clamping-parity, load-filaments-count-exceeds-project, mismatched-extruder-geometry-arrays, export-settings-into-missing-dir-silently-noop, partial-load-filaments-variant-key-zero-filled, sparse-user-filament-with-colour-segfault, vector-override-full-length-multi-filament, vector-override-single-value-multi-filament.