fix: ffmpeg version detection and player letterboxing

ffmpeg only accepts -version (single dash); it exits 8 on --version and
writes to stderr, so the status panel reported it missing even when
installed. Version flags are now per-tool and both streams are read.

The player used max-h-full inside a grid, which a 1080x1920 Short
overflowed. Switched to absolute fill with object-contain so portrait
and landscape both letterbox correctly.

Also sized the window to 1180x780 centered, which fits a laptop display.

README.md

@@ -1,7 +1,100 @@
-# Tauri + React + Typescript
+# FlightTube
 
-This template should help get you started developing with Tauri, React and Typescript in Vite.
+A desktop app that merges all your YouTube subscriptions into one newest-first feed,
+downloads the videos you pick, and — when you have no connection — shows only what you
+already downloaded. Built for the flight.
 
-## Recommended IDE Setup
+Tauri 2 · Rust · React · Tailwind CSS 4 · SQLite
 
-- [VS Code](https://code.visualstudio.com/) + [Tauri](https://marketplace.visualstudio.com/items?itemName=tauri-apps.tauri-vscode) + [rust-analyzer](https://marketplace.visualstudio.com/items?itemName=rust-lang.rust-analyzer)
+## How it works
+
+**Subscriptions come from Google Takeout, not the API.** Export *YouTube subscriptions*
+from [Takeout](https://takeout.google.com/) and import the `subscriptions.csv` in
+Settings. No OAuth, no API key, no Google Cloud project, nothing secret on disk.
+
+**Video metadata comes from YouTube's public Atom feed** — one request per channel to
+`youtube.com/feeds/videos.xml?channel_id=…`, fetched 8 at a time and merged into a single
+feed sorted by publish date. Thumbnails are mirrored to local disk so the feed still
+renders with no network.
+
+**Downloads shell out to `yt-dlp`,** pinned to H.264 video + AAC audio in an MP4
+container. That caps quality at 1080p — YouTube only serves H.264 that high, and anything
+above it is VP9 or AV1, which the app's own player cannot reliably decode. The tradeoff is
+deliberate: every download is guaranteed to play inside FlightTube.
+
+## Requirements
+
+```bash
+brew install yt-dlp ffmpeg
+```
+
+Both are checked at startup; Settings shows their versions and this command if either is
+missing. `ffmpeg` is required because best-quality H.264 and AAC arrive as separate
+streams that must be merged.
+
+## Running it
+
+```bash
+npm install && npm run tauri dev
+```
+
+Build a real app bundle:
+
+```bash
+npm run tauri build
+```
+
+## Using it
+
+1. **Settings → Import subscriptions.csv** — point it at your Takeout export.
+2. **Refresh** — pulls the latest videos from every channel.
+3. **Download** on any video — progress shows live on the button; click again to cancel.
+4. Click a **downloaded** video to play it in the app. Click an undownloaded one to open
+   it on YouTube.
+5. **Offline** — the app detects a lost connection and collapses the feed to your
+   downloads. The connectivity pill also toggles a forced offline mode for testing.
+
+Videos land in `~/Movies/FlightTube` (changeable in Settings).
+
+## Limitations
+
+- The Atom feed returns only the **~15 most recent videos per channel**. There is no
+  backfill and no pagination — this is a rolling recent window, not an archive.
+- Quality tops out at 1080p, by the deliberate choice described above.
+- `yt-dlp` needs occasional updating (`brew upgrade yt-dlp`) as YouTube changes.
+- Downloading videos is contrary to YouTube's Terms of Service.
+
+## Tests
+
+```bash
+cd src-tauri && cargo test
+```
+
+37 unit tests cover the three places malformed input actually bites: Takeout CSV parsing,
+Atom feed parsing (against a captured real response), and `yt-dlp` progress-line parsing —
+plus the database rule that a refresh must never clobber download state.
+
+Two network-dependent tests are excluded by default:
+
+```bash
+cargo test --test pipeline -- --ignored --nocapture      # full pipeline vs. live feeds
+cargo test --test seed_real_db -- --ignored --nocapture  # populate the installed app's db
+```
+
+## Layout
+
+```
+src-tauri/src/
+  takeout.rs     subscriptions.csv -> channels        (pure, tested)
+  feed.rs        Atom XML -> videos, plus fetching    (parse is pure, tested)
+  downloader.rs  yt-dlp arguments and progress lines  (pure, tested)
+  db.rs          schema and every SQL statement
+  thumbs.rs      local thumbnail cache
+  net.rs         reachability probe
+  commands.rs    Tauri command surface — delegates only
+src/
+  components/    Sidebar, TopBar, VideoRow, DownloadButton, Player, Settings
+  hooks/         useFeed, useDownloads, useConnectivity
+```
+
+Design notes and the implementation plan are in `docs/superpowers/`.