GitLab

- 20 unit tests for deriveOpenAIContentSessionSeed covering:
  - Empty/nil inputs, model-only, stable across turns
  - Different model/system/first-user produce different seeds
  - Tools, functions, developer role, structured content
  - Responses API: input string, input array, instructions, input_text typed items
  - JSON canonicalization (whitespace/key-order insensitive)
  - Prefix presence, empty tools ignored, messages preferred over input
- 3 integration tests for GenerateSessionHash content fallback:
  - Content fallback produces stable hash
  - Explicit signals override content fallback
  - Empty body still returns empty hash