fix(miner-insights): render insight description body in Insights & Next Actions card

[Khaostica]

Summary

The Insights & Next Actions card on every miner detail page silently dropped the description body under each insight. Each row rendered only the title + colored type chip (WARNING / TIP / ACHIEVEMENT) with empty space below it, removing all the actionable context users rely on.

Root cause: MinerInsightsCard.tsx had a self-closing <Typography sx={{...}} /> where {insight.description} was supposed to be rendered. The InsightItem interface declared description: string and all 8 insight builders (PR-mode + issue-mode) populated it correctly, but the JSX never emitted a child for it — so the styled <p> sat empty in the DOM on every row.

The fix is a one-line render change. The remaining diff extracts the pure insight-builder logic out of the JSX file into src/components/miners/minerInsights.ts so each builder can be unit-tested without standing up React DOM testing infrastructure (matching the existing src/tests/*.test.ts pure-logic convention). The new test file pins every builder's description-populating behavior so this regression cannot silently come back.

Changes

• src/components/miners/MinerInsightsCard.tsx — adds {insight.description} as a child of the previously self-closing Typography. Removes the inlined insight builders/assemblers (now imported from ./minerInsights).
• src/components/miners/minerInsights.ts (new) — pure module exporting InsightItem, InsightType, the 8 builders (getOpenPrInsight, getCredibilityInsight, getEligibilityInsight, getCollateralInsight, getOpenIssueRiskInsight, getIssueEligibilityInsight, getIssueCredibilityInsight, getIssueSolvedInsight), and assemblePrInsights / assembleIssueInsights. Behavior is identical to the previous inlined implementation — code was moved verbatim.
• src/tests/minerInsights.test.ts (new) — 10 Vitest cases following the pure-logic pattern of the existing tests in src/tests/. Covers every builder and asserts both assemble-level outputs contain only insights with non-empty descriptions.

Related Issues

Closes #1182

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (describe below)

Screenshots

Before:

After:

Checklist

• New components are modularized/separated where sensible
• Uses predefined theme (e.g. no hardcoded colors) — no styling changes; existing STATUS_COLORS + alpha() only
• Responsive/mobile checked — render-only fix, no layout impact
• Tested against the test API
• npm run format and npm run lint:fix have been run
• npm run build passes
• Screenshots included for any UI/visual changes