feat(header): improve sticky header with dynamic scroll tracking

[rohitpaulk]

Remove the old sticky section component and replace it with a unified header
component that tracks scroll position using an in-viewport marker. Introduce a
tracked property to determine stickiness and update the UI accordingly.

Enhance the header template with richer course stage and step status display,
including progress indicators and improved styling for current steps. These
changes improve UX by providing clearer visual context and smoother sticky
header behavior on scroll.

---

Note

Unifies the course page header into a single component with in-viewport-based sticky behavior, removes legacy sections/step switcher, and updates templates accordingly.

• Header:
  • Unifies header by replacing CoursePage::Header::MainSection and CoursePage::Header::StickySection with a single CoursePage::Header (index.hbs/index.ts).
  • Adds in-viewport scroll marker with @tracked state and isSticky getter to control sticky styling and content.
  • Renders TabList, step title/slug, StepStatusPill, and conditional StepProgressIndicator in the unified template.
• Navigation Controls:
  • Simplifies CoursePage::Header::NavigationControls by removing StepSwitcherContainer and badge/label logic; retains menu toggle, dark mode toggle, billing badge, and close button.
• Removals:
  • Deletes CoursePage::Header::MainSection, CoursePage::Header::StickySection, and CoursePage::StepSwitcherContainer (templates and classes).
• Template Integration:
  • Updates app/templates/course.hbs to use CoursePage::Header directly (removes separate main/sticky section usages).

^{Written by Cursor Bugbot for commit 16c9537. This will update automatically on new commits. Configure here.}

[github-actions]

Test Results

  1 files  ±0    1 suites  ±0   9m 2s ⏱️ - 5m 16s
677 tests ±0  624 ✅  - 1  51 💤 ±0  0 ❌ ±0  2 🔥 +1 
677 runs  ±0  622 ✅  - 2  51 💤 ±0  2 ❌ +1  2 🔥 +1 

For more details on these errors, see this check.

Results for commit 16c9537. ± Comparison against base commit 4fae0cd.

♻️ This comment has been updated with latest results.

[codecov]

Bundle Report

Changes will decrease total bundle size by 5.02kB (-0.01%) ⬇️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
client-array-push	38.71MB	-5.02kB (-0.01%) ⬇️

Affected Assets, Files, and Routes:

view changes for bundle: client-array-push

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
assets/chunk.*.js	-110 bytes	3.29MB	-0.0%
assets/chunk.*.js	-4.88kB	399.34kB	-1.21%
assets/chunk.*.css	-38 bytes	250.77kB	-0.02%

[codecov]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
626	2	624	51

View the top 2 failed test(s) by shortest run time

Chrome 140.0::Acceptance | course-page | view-course-stages-test: beta label renders properly

Stack Traces | 0.8s run time

Promise rejected during "beta label renders properly": Element not found.

PageObject: 'page.betaLabelText'
  Selector: '[data-test-course-beta-label]'

Chrome 140.0::Acceptance | course-page | view-course-stages-test: free label renders properly

Stack Traces | 0.833s run time

Promise rejected during "free label renders properly": Element not found.

PageObject: 'page.freeCourseLabel.text'
  Selector: '[data-test-course-free-label]'

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