Separate Core (Ingest/Library/Chat) from Learning/Career/Projects/Organizer
with a thin divider. Separate Mission Control from Reference/Personal/Business
with a divider after Workspaces. Add Business section label for clarity.

Enhance MathLandingView to show inline navigation for Zero to One
(6 topics) and Prepa ML (8 topics) as clickable pills that link
directly to /math/refresh?track=...&tab=... No sidebar changes.
Math Bridge card kept at bottom.

…ar collapse

Backend:
- Migration 0084: track_resources table, track_type on tracks, color on modules
- Extend curriculum models, loader, store, and API for resource tracks
- Resource tracks skip concept validation, support curated link collections
- New endpoints: GET track resources, GET module resources
- Seed job supports --type filter and skips _ prefixed files

Data:
- 11 resource track YAML files extracted from hardcoded frontend views
- 569 resources across 79 modules seeded into database
- Tracks: AI Engineering, Frontend Eng, GPU for AI, Embodied AI,
  Bio-Augmentation, Databases, Applied Systems, Interview Prep,
  Freelance Strategy, Cognitive Toolkit, Behavioral Design
- Displaced prep resources saved in _prep-displaced.yaml for merging

Frontend:
- Generic TrackDetailView handles both concept and resource tracks
- Resource tracks render with tabbed modules and ResourceCards
- CurriculumTracksView shows both track types with correct metadata
- Sidebar collapsed: removed entire Reference section (~1,300 lines)
- Removed Lenses, Levels, Cognitive Toolkit, Behavioral Design from nav
- Added Dev Reference nav item linking to existing dev-ref page
- Added inline tab navigators to DevRefView and DomainOntologyView
- Frontend types extended with TrackResource, track_type, color fields

Delete the entire math feature family: /math, /math/refresh, /math/bridge
and legacy redirects /math-refresh, /math-bridge.

Removes 22 math-only files (views, routes, components, hooks, data),
cleans sidebar nav, route tree, ViewId entries, workflow inventory,
command palette, reference sections, and landing page references.

MathRenderer.tsx preserved (moved to components/) - still used by
culture-generale and ConceptDetailView.

…k ordering

…ion fallback

Curriculum YAML cleanup from product audit:
- Track 1: remove remedial concepts (number, fraction), merge redundant
  concepts (sample-mean, deviation-from-mean, squared-error, l1-reg),
  add one-hot-encoding and normalization-scaling to Module 9
- Track 2: swap Retrieval before Ranking (pipeline order), remove
  feature-store (canonical home is Track 4), add embedding prerequisite
- Track 3: remove etl-vs-elt (redundant with Track 4), merge
  alerting-thresholds and model-rollback into neighbors
- Track 5: rename batch-vs-real-time-serving to match Track 3 naming

Create 5 missing canonical concepts with minimal dossiers:
embedding, bias-variance-tradeoff, one-hot-encoding,
normalization-scaling, regularization

Fix concept explanation fallback to be dossier-first:
- Fetch dossier before attempting retrieval
- Dossier-only concepts produce real explanations (no dead-end)
- LLM fallback when neither dossier nor sources exist
- Three explicit provenance modes in API and UI:
  dossier+retrieval, dossier_only, llm_fallback

Test fixture was using old schema (sort_order column, no track_type/
category/color). Updated to match current production tables. Also
updated stale YAML assertions for ml-foundations (9 modules, not 3).

…e_concepts

Fixes ruff F401 (unused `field` import) and E741 (ambiguous `l` variable).