Resolution dropdown, list-focus preservation, unified dark theme, startup logging, and memory map

- Bottom-bar resolution dropdown (1080p60/1080p30/720p60/480p30) with tooltip
  on finding upload bandwidth; disabled while live; no in-app speed test
- FocusPreservingListBox keeps selection/focus coherent when a selected
  scene/source is deleted (skip hidden scenes; leave list when empty)
- Themes/Controls.xaml: single dark-theme dictionary merged once in App.xaml;
  custom ComboBox template fixes SelectionBoxItem rendering; GoLiveWindow and
  ReuseImageDialog consolidated onto shared styles
- AppLog file logger + AppDomain/Dispatcher exception hooks; checkpointed
  MainWindow/VM/dialog constructors (caught MenuItemRole.Separator XAML crash)
- Memory map: schema.md conventions, per-directory index.md, updated ai.md/
  TASKS.md/README.md (OAuth creds real; token persistence still pending)

schema.md

@@ -0,0 +1,54 @@
+# ytLlive — Memory Map (schema)
+
+This file defines how the repo stores durable, associative memory: context as
+plain markdown files, versioned in git. It is the map of the map — the schema
+that every other memory file follows. Read `ai.md` first; this file explains
+*why* and *how*.
+
+## Why markdown files, not a database
+
+- Grep-able, diffable, portable, human-editable — no tooling lock-in.
+- Git gives versioning and history for free; every stale fact is a `git log` away.
+- Files form a graph: each file is a node, each relative link an edge. The map
+  stays associative (like memory) rather than a rigid tree.
+
+## File inventory
+
+| File | Role | Entry point? |
+|------|------|--------------|
+| `README.md` | Human-facing intro: what the app is, how to run it, roadmap | no |
+| `ai.md` | **AI guide + session handoff** — architecture, patterns, decisions, the cognitive map home | **yes — start here** |
+| `TASKS.md` | Task queue + authoritative YouTube API research facts + task statuses | yes — for status |
+| `schema.md` | This file: the conventions below | when in doubt |
+| `<dir>/index.md` | Per-directory map (progressive disclosure): what lives there + links | when diving into code |
+| `Views/` | Reserved for Views; currently empty | — |
+
+## Conventions
+
+1. **Semantic filenames.** A file's name says what it is (`YouTubeAuthService.cs`,
+   `FocusPreservingListBox.cs`). No codes, no abbreviations. Naming beats search.
+2. **One `index.md` per code directory.** The index is a Map of Content (MOC):
+   it lists every file in that directory with a one-line purpose and links out to
+   related directories. Details live in the files, never duplicated in the index.
+3. **Links over hierarchy.** Prefer relative links between related files over
+   deep nesting. Relationships that matter should be visible from `ai.md` or an
+   `index.md`; a note that is unreachable from `ai.md` might as well not exist.
+4. **Stale facts get FIXED, not appended.** A wrong map is worse than no map.
+   When the code changes, update the memory file in the same change — no
+   "TODO: update later" notes.
+5. **Progressive disclosure.** Don't cram detail into `ai.md`. `ai.md` names
+   concepts and points at files; the indexes and source are the detail. Each
+   layer adds resolution only when you drill in.
+
+## Reading order
+
+1. `ai.md` — what this app is, how it's built, current state, open decisions.
+2. `TASKS.md` — what's done, what's next, and the YouTube API constraints.
+3. `<dir>/index.md` — to understand a directory before reading its files.
+4. The source files themselves — always the authority over any memory file.
+
+## Integration rule
+
+Every feature change ships with its memory update: `ai.md` for architecture /
+patterns, `TASKS.md` for status, index files when the layout changes. That is
+what keeps the map accurate enough to trust next session.