docs: add stats dashboard design docs, plans, and knowledge base

- Stats dashboard redesign design and implementation plans
- Episode detail and Anki card link design
- Internal knowledge base restructure
- Backlog tasks for testing, verification, and occurrence tracking

docs/knowledge-base/quality.md

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+<!-- read_when: assessing architecture health, doc gaps, or where cleanup effort should go next -->
+
+# Quality Scorecard
+
+Status: active  
+Last verified: 2026-03-13  
+Owner: Kyle Yasuda  
+Read when: triaging internal quality gaps or deciding where follow-up work is needed
+
+Grades are directional, not ceremonial. The point is to keep gaps visible.
+
+## Product / Runtime Domains
+
+| Area | Grade | Notes |
+| --- | --- | --- |
+| Desktop runtime composition | B | strong modularization; still easy for `main` wiring drift to reappear |
+| Launcher CLI | B | focused surface; generated/stale artifact hazards need constant guarding |
+| mpv plugin | B | modular, but Lua/runtime coupling still specialized |
+| Overlay renderer | B | improved modularity; interaction complexity remains |
+| Config system | A- | clear defaults/definitions split and good validation surface |
+| Immersion / AniList / Jellyfin surfaces | B- | growing product scope; ownership spans multiple services |
+| Internal docs system | B | new structure in place; needs habitual maintenance |
+| Public docs site | B | strong user docs; must stay separate from internal KB |
+
+## Architectural Layers
+
+| Layer | Grade | Notes |
+| --- | --- | --- |
+| `src/main.ts` composition root | B | direction good; still needs vigilance against logic creep |
+| `src/main/` runtime adapters | B | mostly clear; can accumulate wiring debt |
+| `src/core/services/` | B+ | good extraction pattern; some domains remain broad |
+| `src/renderer/` | B | cleaner than before; UI/runtime behavior still dense |
+| `launcher/` | B | clear command boundaries |
+| `docs/` internal KB | B | structure exists; enforcement now guards core rules |
+
+## Current Gaps
+
+- Some deep architecture detail still lives in `docs-site/architecture.md` and may merit later migration.
+- Quality grading is manual and should be refreshed when major refactors land.
+- Active plans can accumulate without lifecycle cleanup if humans do not prune them.