Add ingestion classifier unit tests for candidate kind mapping

[BennettSchwartz]

Summary

pkg/ingestion/classifier.go has no focused unit tests for Classifier.Classify, which maps ingestion candidate kinds to memory types.

Why this is a good first issue

• Small surface area.
• Deterministic logic.
• Easy to verify with table-driven tests.

Proposed work

Add pkg/ingestion/classifier_test.go covering:

• Event -> episodic
• Tool output -> episodic
• Observation -> semantic
• Outcome -> episodic
• Working state -> working
• Unknown kind -> default episodic

Acceptance criteria

• Tests pass with go test ./pkg/ingestion.
• All CandidateKind values are covered.
• Unknown/default behavior is explicitly asserted.