fix(pwa,tracking): toast race condition, scroll setState deduplication, activeCourseMeta lookup trim consistency

[Copilot]

Three correctness/perf bugs identified in PR review thread #582, addressed together.

Description

useBackToExit — toast callback race condition
When showExitToast() dismissed an old toast and immediately created a new one, Sonner's async exit animation could fire the old toast's onDismiss/onAutoClose after the new toast was registered, resetting firstBackTimeRef, exitArmedRef, and exitModeRef for the live toast. Fixed by capturing the toast id in a closure and guarding clearState() behind an identity check:

let newToastId: ReturnType<typeof toast> | null = null;
const handleClear = () => {
  if (toastIdRef.current === newToastId) clearState();
};
newToastId = toast("Press back again to exit", {
  duration: THRESHOLD_MS,
  onDismiss: handleClear,
  onAutoClose: handleClear,
});
toastIdRef.current = newToastId;

TrackingClient — scroll/resize handler redundant re-renders
updateActiveCourse called setActiveCourseKey + setShowPinnedCourse unconditionally on every scroll/resize event, even when the computed value was unchanged. Added lastActiveCourseKeyRef / lastShowPinnedCourseRef to gate setState to actual changes. Also wrapped the event handler in requestAnimationFrame throttling so rapid bursts incur at most one layout read + setState per frame.

TrackingClient — activeCourseMeta lookup trim mismatch
displayCourseName and courseCode were looked up using items[0].course (raw, untrimmed) while grouping keys are keyed on item.course.trim(). Replaced with activeCourseKey (already trimmed) to guarantee lookup hits.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Performance improvement
• Test updates

Related Issues

Relates to #582

Changes Made

• src/hooks/useBackToExit.ts: scope onDismiss/onAutoClose callbacks to their toast id via closure guard to prevent stale callbacks clearing active toast state
• src/app/(protected)/tracking/TrackingClient.tsx: add lastActiveCourseKeyRef + lastShowPinnedCourseRef; gate setActiveCourseKey/setShowPinnedCourse to value changes only; add RAF throttle on scroll/resize handler
• src/app/(protected)/tracking/TrackingClient.tsx: use activeCourseKey (trimmed) instead of items[0].course for attendanceData/coursesData lookups in activeCourseMeta

Version Bump

• Version automatically bumped by workflow (same-repo PRs)
• Version manually bumped using node scripts/bump-version.js (fork PRs)
• Version already up-to-date (no bump needed)

Testing

Test Environment

• Node version: 22.x
• npm version: 10.x
• OS: Linux

Tests Performed

• Unit tests pass (npm run test)
• E2E tests pass (npm run test:e2e)
• Linting passes (npm run lint)
• Manual testing completed

Test Coverage

30 existing unit tests across useBackToExit and TrackingClient suites pass with no modifications required.

Documentation

• Documentation updated (if needed)
• Code comments added for complex logic
• API documentation updated (if API changes)

Checklist

• My code follows the project's code style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Screenshots (if applicable)

N/A — logic-only changes, no UI visual delta.

Additional Notes

The newToastId = null initialization in showExitToast is intentional: handleClear must capture the variable by reference (not value) before toast() is called, making a let + deferred assignment the only viable pattern for this circular closure dependency.

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For maintainers:

• PR title follows conventional commit format
• Version bump is correct
• All checks pass
• Documentation is complete
• Ready to merge

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[Copilot]

Pull request overview

This PR fixes a couple of correctness edge cases and reduces unnecessary rendering work in PWA/back-navigation and the tracking page, improving stability and scroll performance in GhostClass.

Changes:

• Prevents stale Sonner toast callbacks from clearing state for a newer “press back again to exit” toast in useBackToExit.
• Deduplicates scroll/resize-driven React state updates and throttles the active-course header computation with requestAnimationFrame.
• Fixes activeCourseMeta lookups to use the trimmed activeCourseKey consistently.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/hooks/useBackToExit.ts	Guards toast clear callbacks by toast-id identity to avoid race conditions during dismiss/create cycles.
src/app/(protected)/tracking/TrackingClient.tsx	Adds RAF throttling + last-value refs to avoid redundant re-renders and ensures trimmed key is used for active course metadata lookups.