[hannahlanzrath]

Summary

• New .github/workflows/tests.yml: conda (via environment.yml, for the real CADET-Core binary) + a pinned CADET-Process dev-branch commit + headless Chromium, then pytest -v. Runs on push to main and on every PR.
• Real bug fixed: pyproject.toml declared the dependency as CADETProcess (the import name); the published distribution name is CADET-Process (hyphenated), and PEP 503 normalizes these to different names, so this dependency could never resolve — not in CI, not anywhere. Fixed to CADET-Process>=0.11.
• CADET-Process pin: no released CADET-Process version includes CADETProcess.instruments (the LC flow-sheet layer this GUI's whole architecture sits on) or the column/binding descriptor unit=/description= metadata (upstream PR #435) that several tests depend on. Both exist on CADET-Process's dev branch; pinned to its current commit (a064f9c) rather than floating on the branch tip, for reproducibility. This is a real, current constraint — CADET-GUI depends on not-yet-released CADET-Process features — and will need revisiting once CADET-Process cuts a release that includes them.
• Added playwright to the testing/dev dependency groups and a Chromium install step: tests/test_element_views.py's headless-browser element tests were silently skipping everywhere (locally and would have in CI) for lack of a browser. They now actually run — 32+ tests that were never exercised.
• ruff.yml's push trigger listed master/dev (stale, inherited from a template); this repo's real branch is main. Fixed both workflows to trigger on push to main.

Verified by building the exact environment environment.yml + these install steps produce, from scratch, in an isolated conda env: 588 passed, 0 failed, 0 skipped.

Test plan

• Full suite verified locally in a from-scratch conda env matching the workflow exactly (588 passed)
• ruff check clean
• YAML/TOML validated