fix: invalid gene check

[joyceyan]

Reason for Change

https://czi-sci.slack.com/archives/C07AV4NU9D2/p1755897599662919?thread_ts=1755889725.833399&cid=C07AV4NU9D2

Changes

• replaces return with continue, so that we append errors for each invalid gene

Testing

updated an existing test we had to ensure we would return 2 errors for 2 invalid genes

Notes for Reviewer

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.99%. Comparing base (68f1b39) to head (610fe11).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1432      +/-   ##
==========================================
- Coverage   89.03%   88.99%   -0.04%     
==========================================
  Files          23       23              
  Lines        2580     2580              
==========================================
- Hits         2297     2296       -1     
- Misses        283      284       +1     

Components	Coverage Δ
cellxgene_schema_cli	89.48% <100.00%> (-0.06%)	⬇️
migration_assistant	91.26% <ø> (ø)
schema_bump_dry_run_genes	79.74% <ø> (ø)
schema_bump_dry_run_ontologies	99.51% <ø> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.