normalization-atomicity

Normalization atomicity — all persisted data must be canonicalized

Any value written to Firestore (or any persistent store) must pass through its canonicalizer before persistence — regardless of which execution path performs the write.

Specific case: rewards_box dicts written to Firestore must pass through normalize_rewards_box_for_ui() (or rewards_engine.canonicalize_rewards()) before being stored. "Passthrough", "passthru", and "passthrough" path names are semantically misleading — they imply no transformation but persistence requires canonicalization.

Correct pattern:

• Streaming path → llm_parser.py → calls canonicalize_rewards() → normalized output persisted
• Polling path → project_level_up_ui() → normalized output stored
• Passthrough path → must still call normalize_rewards_box_for_ui() before persisting

Why: PR #6265 fixed the passthrough branch when _has_level_up_ui_signal was False — the raw LLM rewards_box was returned without normalization. A path labeled "passthrough" does not mean "skip normalization."