feat(core): R-05 PR2 alpha aggregation policy

[lemone112]

R-05 PR2: Alpha aggregation types + pure function.

No R-04/R-09 runtime dependency (pure aggregation only).
Depends on: R-05 PR1 (BackdropContextV1)
Blocks: R-05 PR3-4, R-06 PR3.

Types

• AlphaAggregationPolicyV1: validated aggregation policy (WeightedAverageWithFloor variant)
• AggregatedAlphaCleanEvidenceV1: aggregated evidence carrier
• aggregate_alpha_clean_evidence(): pure function with fixed-point arithmetic

Invariants

• All-transparent input yields 0 contribution (not default-clean)
• Floor prevents clean masking of dirty opaque
• Zero unwrap in production paths
• pub(crate) with #[expect(dead_code)] per V7 staging

Tests

11 tests (8 unit + 3 property: monotonicity, floor invariant, empty-input)

Files

• crates/labcolors-core/src/alpha_assessment.rs — AlphaCleanPotentialAssessmentV1, BackdropContextV1, LayerIdentityV1, compute_weighted_contribution()
• crates/labcolors-core/src/alpha_aggregation.rs — AlphaAggregationPolicyV1, AggregatedAlphaCleanEvidenceV1, aggregate_alpha_clean_evidence()
• crates/labcolors-core/src/mod.rs — module wiring

[coderabbitai]

Warning

Review limit reached

You’ve reached a temporary PR review limit under our Fair Usage Limits Policy.

Your current included review allowance is based on your included PR review attempts over the past 7 days.

Next review available in: 20 minutes

Limit details: You’ve used the included review currently available. Your 101 included PR review attempts over the past 7 days set your current allowance at 1 review per hour.

Enable usage-based reviews in Billing to review now. Otherwise, wait until the next included review is available.
You're only billed for reviews past your plan's rate limits ($0.25/file).

How can I continue?

Wait for the limit to reset, then comment @coderabbitai review or push new commits to the PR.

An organization admin can change what happens after included review limits in Billing.

How do review limits work?

CodeRabbit enforces per-developer PR review limits within each organization.

For paid Pro and Pro+ reviews, CodeRabbit uses a developer's included PR review attempts over the past 7 days to set the current hourly allowance. At typical activity levels, the full plan allowance applies. Higher sustained activity can lower the allowance until earlier attempts leave the 7-day window.

Please refer docs for additional details.

Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: d271b560-effb-4b09-a34d-d3297a3f0915

📥 Commits

Reviewing files that changed from the base of the PR and between da6f2d6 and d4d90e0.

📒 Files selected for processing (8)

• crates/labcolors-core/contracts/clean-set-srgb8-v1/receipt-v1.json
• crates/labcolors-core/contracts/clean-set-srgb8-v1/receipt-v1.sha256
• crates/labcolors-core/contracts/point-support-reference-surplus-q55-bps-proof-v1.json
• crates/labcolors-core/src/cleanliness/alpha_aggregation.rs
• crates/labcolors-core/src/cleanliness/alpha_assessment.rs
• crates/labcolors-core/src/cleanliness/mod.rs
• crates/labcolors-core/src/lib.rs
• scripts/verify_point_support_surplus.py

---

_{Comment @coderabbitai help to get the list of available commands.}