Enable react-hooks/rules-of-hooks as an error

[tomsmith8]

Summary

react-hooks/rules-of-hooks was set to "off" in eslint.config.mjs, which let a conditional useMemo ship in RecursionBox (since fixed). This turns the rule back on as an error and fixes the 12 existing violations so npm run lint passes.

Changes

• eslint.config.mjs: flip react-hooks/rules-of-hooks from off to error in the global rules block. The test-file override that disables the rule for __tests__ and *.test.* is unchanged.
• ScreenshotModal: move the keyboard-navigation useEffect and its derived index values above the if (!screenshot) return null guard. The effect now bails when there is no screenshot, matching the previous behaviour.
• ClarifyingQuestionsPreview: move the answers and showReview state, the submit-button ref, and its focus effect above the empty-questions early return.
• WorkflowVersionList: move the version grouping and expandedGroups state above the empty-list early return. groupWorkflowVersions already handles an empty array.
• LineComponent: rename the inner _LineComponent to LineComponentBase. The leading underscore made the rule treat it as a plain function rather than a component. displayName and the memo export are unchanged.

Verification

• npm run lint: 0 errors (265 pre-existing warnings, unchanged).
• npx tsc --noEmit: no errors in the touched files.