Add AGENTS.md on-ramp, response-style rules, and optional No-Fluff Mode

- AGENTS.md: auto-read session on-ramp — memory-map reading order, working
  rules, build command, and startup-log pointer
- ai.md: Response style section (no default planning boilerplate) plus an
  optional, on-demand No-Fluff Mode for ruthless review; never the default
- schema.md: AGENTS.md listed as the always-read first page

AGENTS.md

@@ -0,0 +1,38 @@
+# AGENTS — how to work in this repo
+
+This file is auto-read at the start of every session. The project keeps its
+memory as a linked map of markdown files — read it before doing anything.
+
+## Onboarding (in order)
+
+1. [`schema.md`](schema.md) — the memory-map conventions (what lives where, how to keep it true).
+2. [`ai.md`](ai.md) — the AI guide: architecture, patterns, decisions, current state.
+3. [`TASKS.md`](TASKS.md) — the task queue + authoritative YouTube API research.
+4. `<dir>/index.md` — the index for any directory you're about to touch.
+
+## Working rules
+
+- **Never work without the map.** If the map contradicts the code, the code wins
+  and the map gets fixed in the same change (stale facts are corrected, not appended).
+- **Every feature change ships with its memory update:** `ai.md` for
+  architecture/patterns, `TASKS.md` for status, index files when layout changes.
+- **Follow existing conventions** — MVVM, `RelayCommand` for actions,
+  `ViewModelBase.SetProperty<T>()`, all styles in `Themes/Controls.xaml`
+  (merged once in `App.xaml`; never duplicate per-window).
+- **Do not add comments unless the code needs them; do not expand the task queue
+  on your own** — work only what the user queues.
+- **Response style: no default planning template.** Do the work, then report
+  what changed and what's next. No "Plans & Pitfalls", pros/cons tables, or
+  step-by-step plans unless the user asks for a plan first (see `ai.md`).
+- **No-Fluff Mode is available on request** — unpadded, ruthless review that
+  argues rather than reassures (see `ai.md`). Optional, never the default.
+
+## Build
+
+```bash
+dotnet build   # Windows-only WPF; builds from WSL via EnableWindowsTargeting
+```
+
+Keep it at **0 warnings**. Running requires Windows. On a silent startup crash,
+read `%APPDATA%\ytLlive\startup.log` (`Helpers/AppLog.cs` writes checkpoints and
+unhandled exceptions there).