refactor: gate CourseBreadcrumbs on the queries

[brian-smith-tcril]

Summary

Gate CourseBreadcrumbs on the queries instead of the Redux status strings: useIsCourseLoaded(courseId) and useSequenceMetadata(sequenceId).isSuccess replace the slice's 'loaded' && 'loaded' comparison — both ids were already props. This is layer A4 (of six) of the courseware slice teardown #1976 (plan), stacked on the loaded-gate layer #2071, and deliberately tiny: one consumer whose inputs both exist. Part of #1976 — the teardown's final layer closes it.

With this, the transitional status bridge's only remaining readers are CoursewareContainer and TabPage — exactly the surface of the two teardown layers that follow.

What changed

• CourseBreadcrumbs.jsx: the two useSelector status reads become the query gates; the useMemo deps follow; react-redux leaves the file. Model reads (useModel/useModels) untouched — read conversions are Dissolve the model-store normalized cache #1977's home.
• CourseBreadcrumbs.test.jsx: gains the QueryClientProvider the component now needs and async settles on the loaded-gated assertions. Its pre-existing /preview/courses pathname cases now genuinely exercise the preview-keyed sequence query (useSequenceMetadata derives isPreview from the pathname, refactor: derive sequence status from the sequence query #2070).

Testing

npm run types (0 errors), npm run lint (clean), full jest suite green at head (111 suites, 1131 passed / 3 pre-existing skips). Manual pass on tutor local in the details block below — including a note on a pre-existing jump-nav preview-prefix gap observed while testing (untouched by this stack, not filed per review).

Decisions

Full decision log

Decisions — CourseBreadcrumbs onto the query gates (#1976, layer A4)

1. Pure consumer swap. CourseBreadcrumbs gates its breadcrumb links on
   useIsCourseLoaded(courseId) && useSequenceMetadata(sequenceId).isSuccess
   instead of the slice's 'loaded' && 'loaded' strings — both ids were
   already props. The useMemo deps swap the two strings for the two
   booleans. react-redux leaves the file. Model reads (useModel/
   useModels for the course/sections/sequences) are untouched — Dissolve the model-store normalized cache #1977's
   home.

2. Kept as its own tiny layer rather than folding into A3: the layer
   boundary is "one consumer, both inputs already exist", and the diff reads
   in one screen.

3. Tests: the suite gains the QueryClientProvider the component now
   needs and async settles (findAllByTestId/findByText) for the
   loaded-gated assertions. Its pre-existing /preview/courses pathname
   cases now genuinely exercise the preview-keyed sequence query
   (useSequenceMetadata derives isPreview from the pathname);
   initializeTestStore's sequence mock matches either preview param.

4. Behavior deltas: the standard posture (the component's own query
   subscriptions; results bridge into the model store as before). Otherwise
   faithful: same gate, same render output.

Manual testing

Manual testing — CourseBreadcrumbs onto the query gates (#1976, layer A4)

In-browser verification for layer A4, against tutor local
(http://apps.local.openedx.io:2000/learning, DemoX). This layer claims
zero user-facing change: breadcrumbs gate on the queries instead of the
Redux status strings.

Verify by hand

• Breadcrumbs render — CourseBreadcrumbs only renders through the
  org.openedx.frontend.learning.course_breadcrumbs.v1 slot, which is empty
  by default: re-inject the default component via env.config.jsx per the
  slot's README first. Then open a unit: the breadcrumb bar shows Course home
  plus the section and sequence crumbs once loaded; the section/sequence
  dropdowns navigate.

Results

The render check passed (2026-09-16, tutor local, DemoX, default breadcrumbs
re-injected via env.config.jsx, run against the local branch @ 05c90e75):
crumbs render once loaded and the dropdowns navigate.

A preview-route check was dropped: with jump nav enabled (the staff/preview
context), crumb clicks go through JumpNavMenuItem.destinationUrl(), which
has never carried the /preview prefix — pre-existing on master (neither
BreadcrumbItem.tsx nor JumpNavMenuItem.jsx changes in this stack), so it
can't verify this layer. Not filed, per review.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.77%. Comparing base (05011cb) to head (05c90e7).

Additional details and impacted files

@@                          Coverage Diff                          @@
##           bsmith/course-loaded-sequence-ids    #2072      +/-   ##
=====================================================================
- Coverage                              93.77%   93.77%   -0.01%     
=====================================================================
  Files                                    367      367              
  Lines                                   6039     6038       -1     
  Branches                                1428     1395      -33     
=====================================================================
- Hits                                    5663     5662       -1     
- Misses                                   359      360       +1     
+ Partials                                  17       16       -1     

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