feat: output schema conformance to spec Section 8
- VelocityMetrics: hype_velocity/pub_velocity range -100 to +100 (was 0-1)
- EventFlag: full spec Section 8.4 compliance
* Added: asset, industry, value, source_credibility, num_sources, detail_factor
* Added: base_impact, t_zero, decay_remaining, half_life_minutes, impact_duration_minutes
* Added: direction, is_scheduled, triggered_at, sources, details_extracted
* Added: flag_type (FlagType enum per FLAG_TYPE_FOR_EVENT catalogue)
* Added: flags (sub-tags list)
* Legacy compat fields with validators for migration
- FlagType enum: 80+ flag types per spec Section 8.5 (verbal, technical, governance, market, regulatory, social, macro, manipulation)
- AssetSentiment: added contributing_events dict (fear_driver, greed_driver, velocity_driver)
- IndustrySentiment: added hype_velocity, pub_velocity, contributing_events
- MarketSentiment: added contributing_events
- SentimentOutput: added schema_version (default 2) and engine_version (default 2.0.0)
- All 46 core NLP unit tests pass
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