Design confidence and uncertainty indicators for Health Dashboard scores

[dzarlax]

Summary

Add a product UI layer that shows score freshness, coverage, and confidence once the serving/freshness contract is implemented.

Original Todoist task: 6gg9WWR8gcqc76Hf
Original due date: 2026-06-11

Background

Phase A is already done: stale_stress was split into data_accruing versus stale_stress. Phase B is the dashboard UI layer. The dashboard should not force users to guess whether a quiet score means everything is OK, data is stale, or confidence is low.

Dependency

Implement the readiness serving/freshness contract first so the UI has reliable fields to render. Do not guess confidence from presentation-only heuristics.

Scope

• Per-score confidence or freshness badges near methodology badges.
• Coverage percentage and low-confidence reason tooltips.
• Positive contra-signal such as fresh data / coverage OK where appropriate.
• Visual dimming only when confidence is actually low.
• Keep UI language concise and understandable for non-technical users.

Acceptance Criteria

• UI distinguishes fresh, stale, low-confidence, and fully covered states.
• Tooltips explain why confidence is low without exposing implementation noise.
• The API contract is documented or covered by tests.
• Mobile and desktop layouts remain readable.
• Relevant frontend/manual QA is documented in the PR.

[dzarlax]

Unblocked for planning after the readiness serving/freshness contract shipped.

Relevant prerequisite now satisfied:

• PR Add readiness serving contract #177 / issue Implement readiness serving and freshness contract before confidence UI #166 delivered the server-owned readiness serving/freshness contract.
• The next step should be a UI implementation plan for confidence/uncertainty indicators, not direct coding.

Label update: status:blocked -> status:needs-plan.