Add tests for classifier.classify() and classifier.classify_pending_filings()

[AshayK003]

Untested functions

classify() (diffiq/classifier.py:30)

Classifies a single filing by type (annual, quarterly, etc.) based on keywords in the title. Needs tests for:

• Annual filing title -> "annual"
• Quarterly filing title -> "quarterly"
• Mixed signals -> correct priority
• Empty title -> default classification
• Non-English keywords

classify_pending_filings() (diffiq/classifier.py:52)

Batch classifies all pending filings in the database. Needs tests for:

• Multiple pending filings -> all classified
• No pending filings -> no-op
• Database error -> graceful handling

How to run

python -m pytest tests/test_classifier.py -v

Difficulty

Easy. Pure logic, no external dependencies.