feat(core): bounded O(1) risk aggregator with normalized context + extended tests

[Ananya44444]

Description:

Implemented a deterministic, O(1) Risk Aggregator that produces a normalized RiskContext aligned with the Phase-1 architecture.

Added explicit weighted scoring model with bounded signal set
Enforced signal normalization and schema constraints to preserve fast-path guarantees
Introduced provenance-aware scoring hooks (non-breaking for v1, extensible for v2)
Added guardrails for fixed signal vector to prevent unbounded growth
Included hook-aware placeholders for future policy tuning without affecting current latency

Tests:

Covered structure, normalization, determinism, and score bounds
Added edge cases for missing/invalid signals
Ensured OPA-compatible input format ({"input": RiskContext})

This keeps the aggregator strictly within the fast-path constraints (<10ms) while aligning with the taxonomy-driven policy layer.

[Copilot]

Pull request overview

Adds a new Python-side “risk context” contract and deterministic O(1) risk aggregation helper intended to produce an OPA-compatible input object, along with a dedicated test suite validating shape, normalization, determinism, and score bounds.

Changes:

• Introduces acf.sdk_integration.risk_context with fixed-signal normalization, weighted scoring, and hook/provenance adjustments.
• Adds acf.sdk_integration package exports for the new aggregator surface.
• Adds pytest coverage for structure, normalization, determinism, and defaulting behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
sdk/python/acf/sdk_integration/risk_context.py	Implements RiskContext + aggregate_risk with fixed-size normalization and scoring.
sdk/python/acf/sdk_integration/init.py	Exposes RiskContext and aggregate_risk as package-level API.
sdk/python/tests/test_risk_context.py	Adds tests for shape/normalization/determinism/score bounds for the new aggregator.

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