Description

Removes the entire legacy (non-MFE) course search frontend, completing DEPR #39089.

Deleted / changed:

• The openedx/features/course_search/ Backbone/RequireJS bundle in full — both entry points (the unreachable in-course course_search_factory and the dashboard "Search Your Courses" dashboard_search_factory), their shared views/collections/models, Underscore templates, JS spec, and fixtures.
• The two course_search/js/*_factory entries in the RequireJS build manifest (lms/static/lms/js/build.js) and the removed spec from the JS test manifest (lms/static/lms/js/spec/main.js).
• The "Search Your Courses" widget in lms/templates/dashboard.html.
• The ENABLE_DASHBOARD_SEARCH feature flag: its definition in lms/envs/common.py, the env defaults in test.py / devstack.py, and its clause in the SEARCH_ENGINE condition in lms/envs/production.py.

Preserved (out of scope)

• The /search/ endpoint (search.urls), ENABLE_COURSEWARE_SEARCH, and the shared content index — in-course search in the learning MFE depends on them, so removing dashboard search frees no search infrastructure.
• The SCSS search partials (search/_search.scss, search/_instant-search.scss, features/_course-search.scss) are intentionally left in place: their classes are shared with the bookmarks, gradebook, and edxnotes UIs, so pruning any dead rules needs a separate, carefully scoped pass.

Supporting information

• DEPR: [DEPR]: Legacy (non-MFE) course search frontend #39089 (fast-track; Breaking Changes Unblocked 2026-09-10). Supersedes [DEPR]: Cross-course 'Search Your Courses' (dashboard search) #38941.
• The in-course Backbone UI was already unreachable dead code (only the RequireJS build manifest referenced it); the learning MFE is the replacement. Cross-course "Search Your Courses" had no MFE replacement and is removed per the DEPR.
• Tracked in Inventory the current state of the MFEs and Legacy Pages #38936.

Testing instructions

• Legacy dashboard renders without the "Search Your Courses" widget when ENABLE_DASHBOARD_SEARCH was previously set.
• In-course search in the learning MFE still works (unchanged /search/ + ENABLE_COURSEWARE_SEARCH).
• CI confirms nothing references the removed modules/flag.