refactor(processor): nest spectral metrics under shared model

[flexiondotorg]

• Move interval and measurement spectral values into nested SpectralMetrics
• Preserve flat spectral JSON fields for backward compatibility
• Update adaptive, logging, and candidate consumers to read nested values
• Add shared spectral report descriptors and stale-field guard tests

[cubic-dev-ai]

1 issue found across 23 files

Confidence score: 2/5

• There is a high-confidence, high-severity serialization bug in internal/processor/analyzer_metrics.go: promoted MarshalJSON/UnmarshalJSON methods on embedded BaseMeasurements can cause outer measurement structs to read/write only base fields.
• This creates concrete regression risk for metrics payloads, since non-base fields may be silently dropped during JSON marshal/unmarshal and lead to incorrect processing downstream.
• Given the 8/10 severity and 9/10 confidence, this is likely merge-blocking until serialization behavior is corrected.
• Pay close attention to internal/processor/analyzer_metrics.go - embedded-method promotion is likely overriding expected outer struct JSON handling.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="internal/processor/analyzer_metrics.go">

<violation number="1" location="internal/processor/analyzer_metrics.go:196">
P1: Defining MarshalJSON/UnmarshalJSON on embedded BaseMeasurements causes outer measurement structs to serialize/deserialize only base fields due to method promotion.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

0 issues found across 2 files (changes from recent commits).

_{Requires human review: Large-scale refactor of core data models and adaptive logic across many files. Custom JSON marshaling/unmarshaling logic warrants human review to ensure API compatibility and no regressions.}