Version and Register Verification Prompts

[richardgittest]

Files Changed

1. Core registry + prompt library — humanitarian_prompt.py

New PromptVersion (frozen dataclass): name, version, description, immutable builder. Exposes content_hash(**kw) and build(**kw).
New PromptRegistry class:
register(prompt_version) — rejects duplicates → enforces no edit-in-place
set_active_version(name, version) — runtime pinning
get_active_version(name) — falls back to latest registered when config is silent
resolve(name, version=None) — explicit or active lookup
build_prompt(name, version=None, **kw) — returns {system, user, prompt_name, prompt_version, prompt_content_hash}
Default 1.0 versions for both humanitarian_primary and humanitarian_fallback are the exact original prompt texts extracted from the inline builder — semantically identical.
2. Configuration — config.py

New field humanitarian_prompt_active_versions: Dict[str, str] with JSON env var example in docstring.
3. Verification service — humanitarian_verification.py

Constructor now accepts prompt_registry: Optional[PromptRegistry] (defaults to one built from settings).
verify_claim() builds both prompts via registry.build_prompt(...), records prompt_name, prompt_version, prompt_content_hash in the returned dict alongside the existing prompt_variant label.
New get_prompt_versions_tag() → "primary=1.0|fallback=1.0" used as a cache key tag so a version bump auto-invalidates.
4. Response schemas — schemas/common.py and schemas/humanitarian.py

Common: new PromptVersionInfo(name, version, content_hash) model + new optional prompt_versions: Dict[str, PromptVersionInfo] field on ResultEnvelope.
Humanitarian legacy schema: added prompt_name, prompt_version, prompt_content_hash fields + model_config = { "extra": "ignore" } so HumanitarianVerificationResponse(success=True, **result) in the deprecated route stays permissive.
5. Humanitarian API route — api/v1/humanitarian.py

Added prompt_versions_tag to @cached_response key_tags so prompt-version changes bust the cache (no stale responses after rollback/upgrade).
Builds prompt_versions envelope map from raw["prompt_name"] / ["prompt_version"] / ["prompt_content_hash"] keyed by the prompt_variant label ("primary" or "fallback").
6. Regression harness migration — regression_harness/deterministic_provider.py

Replaced HumanitarianPromptEngine() + build_primary_prompt/build_fallback_prompt with PromptRegistry().build_prompt("humanitarian_primary"/"humanitarian_fallback", …). llm_chat still consumes prompt["system"]/prompt["user"] unchanged — behaviour preserved.

Closes #979

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[Cedarich]

@richardgittest kindly fix CI