fix: temp_circadian fabricated 0.0 on flat series

[abdulsaheel]

found during a full-codebase pass. _nonparam() in temp_circadian.dart was
missing the zero-variance guard circadian_np.dart already has — a flat or
heavily-quantized skin-temp window came back with IS=0.0/IV=0.0 like a real
"perfectly stable" reading instead of absent.

also left a ponytail comment on a dormant zero-baseline fallback in
ewma_baselines.dart — unreachable today (no metric has minVal <= 0) so not
worth a real fix, just flagged for later.

660 passing locally (dart test), one new regression test added.

🤖 Generated with Claude Code

Summary by Sourcery

Prevent flat temperature windows from being misreported as valid zero-valued circadian stability metrics.

Bug Fixes:

• Return circadian nonparametric metrics as absent for zero-variance or otherwise undefined flat temperature windows instead of reporting fabricated zero values.

Tests:

• Add regression coverage confirming nonparametric circadian results are withheld for flat temperature series.

Chores:

• Flag the dormant zero-baseline deviation fallback for future review.

Summary by CodeRabbit

• Bug Fixes

  • Improved circadian rhythm analysis for flat or zero-variance temperature data by withholding undefined metrics instead of reporting misleading zero values.
  • Preserved the overall wellness metric when detailed circadian calculations cannot be determined.

• Documentation

  • Clarified baseline deviation behavior when the baseline is exactly zero.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Advanced

Run ID: b64de652-4a07-428e-8b73-8a134061205d

📥 Commits

Reviewing files that changed from the base of the PR and between 01e8b6e and 0c19d86.

📒 Files selected for processing (3)

• lib/src/onehz/foundations/ewma_baselines.dart
• lib/src/onehz/wellness/temp_circadian.dart
• test/onehz/wellness_test.dart

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📝 Walkthrough

Walkthrough

The change treats flat temperature data as undefined for nonparametric circadian metrics, adds regression coverage, and documents zero-baseline behavior in EWMA calculations.

Changes

Metric handling

Layer / File(s)	Summary
Circadian zero-variance handling lib/src/onehz/wellness/temp_circadian.dart, test/onehz/wellness_test.dart	_nonparam returns null when variance or consecutive-difference energy is zero. The test verifies that the overall metric remains available while nonparametric metrics remain absent.
EWMA baseline documentation lib/src/onehz/foundations/ewma_baselines.dart	Documentation describes the 0.0 ratio fallback for an exactly zero baseline and the current constraint that prevents update from creating that baseline.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: preventing fabricated 0.0 values in temp_circadian for flat temperature series.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[sourcery-ai]

Reviewer's Guide

The PR fixes temp circadian analysis so flat or quantized windows produce an absent nonparametric result rather than fabricated IS/IV values of 0.0, adds regression coverage, and documents an unrelated dormant zero-baseline fallback for future review.

Flow diagram for flat temperature circadian handling

flowchart TD
    A[Temperature window] --> B["_nonparam()"]
    B --> C[Compute total variance and difference energy]
    C --> D{varTot == 0 or diffN == 0?}
    D -- Yes --> E[Return absent CircadianNonparam]
    D -- No --> F[Compute IV and IS]
    F --> G[Return CircadianNonparam]

Loading

File-Level Changes

Change	Details	Files
Withhold nonparametric circadian metrics when the input window has no usable variance.	Return null before IS/IV normalization when total variance or consecutive-difference data is unavailable. Remove zero-valued fallback branches that misrepresented undefined divisions as stable readings. Align the guard behavior with the existing nonparametric circadian implementation.	lib/src/onehz/wellness/temp_circadian.dart
Add regression coverage for flat temperature series.	Verify a zero-variance multi-day ADC series leaves the nonparametric result absent while the overall metric remains present.	test/onehz/wellness_test.dart
Document a dormant zero-baseline ratio fallback for future follow-up.	Flag the silent ratio=0 behavior as unreachable with current positive metric ranges and recommend making the ratio nullable if zero-crossing metrics are introduced.	lib/src/onehz/foundations/ewma_baselines.dart

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