Add lab restream pipeline with pirate_drift logo and lib/env.sh.

Encode-once/fanout scripts, HLS output, and single overloadable env source.
Commits assets/pirate_drift.png as default watermark for cluster runs.

Co-authored-by: Cursor <cursoragent@cursor.com>

README.md

@@ -1,3 +1,35 @@
 # ac-ms-media-transcode
 
-Future VOD/transcode. Remote: `git://f0xx.org/ac/ac-ms-media-transcode`
+V.2x lab restream / transcode worker (F2). Shell pipeline: **encode once → HLS + optional RTMP fanout**.
+
+Remote: `git://f0xx.org/ac/ac-ms-media-transcode`
+
+## Layout
+
+| Path | Role |
+|------|------|
+| `lib/env.sh` | **Single config source** — all variables, overload via `export` or `config/local.env` |
+| `assets/pirate_drift.png` | Default logo watermark (committed) |
+| `bin/` | encode-once, fanout-copy, run, probe, … |
+| `config/sources.list` | Lab source URLs |
+| `config/sinks.list` | RTMP publish targets (fanout stage) |
+
+## Lab cluster
+
+Composed BE `config.php` (via `compose-lab-backend.sh`):
+
+- `media_pipelines.enabled` = **true**
+- `script_root` = `/var/www/ac/workspace/ac-ms-media-transcode`
+- `logo_path` = `…/assets/pirate_drift.png`
+- HLS nginx alias = `/app/androidcast_project/media/hls/` → `/var/www/ac/media-pipelines/hls/`
+
+Console UI: `?view=media_pipelines` (global admin / `media_pipelines_*` grants).
+
+## Local override
+
+```bash
+cp config/local.env.example config/local.env
+./bin/run.sh 1
+```
+
+All tunables live in `lib/env.sh` using `export VAR="${VAR:-default}"`.