docs: content-sourcing procedure + roadmap update + setup docstring (content pipeline Increment 1)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/content-sourcing.md

@@ -0,0 +1,29 @@
+# Content sourcing — strict-PD neutral bases
+
+For each scale, acquire a calm, neutral source clip from a **strict public-domain**
+US-government source, verify the license, then run it through the pipeline.
+
+| Scale  | Source                         | Where                              |
+|--------|--------------------------------|------------------------------------|
+| cosmos | NASA / Hubble / JWST           | https://images.nasa.gov/           |
+| orbit  | NASA / ISS                     | https://images.nasa.gov/           |
+| forest | NPS / USGS                     | https://www.nps.gov/ , https://www.usgs.gov/ |
+| reef   | NOAA Ocean Exploration         | https://oceanexplorer.noaa.gov/    |
+| abyss  | NOAA Ocean Exploration         | https://oceanexplorer.noaa.gov/    |
+
+**License check (mandatory):** confirm the asset is US-gov PD (17 U.S.C. §105) or
+explicitly CC0. "Free stock" (Pexels/Pixabay/etc.) is royalty-free but NOT public
+domain — do not use. Record a `Provenance` (tools/pipeline/provenance.py) per clip.
+
+**Run the pipeline** (replaces the placeholder bytes for a scale):
+
+```bash
+python -c "from tools.pipeline.run import process_clip; \
+  process_clip('downloads/<scale>.mp4', 'simulator/sample_media/<scale>', \
+  start=<in_s>, duration=<len_s>, overlap=<0.5..1.0>)"
+```
+
+This writes `simulator/sample_media/<scale>/base.mp4` (proxy) + `master.mp4`. Then
+author the labels (Increment 2: the hybrid track pass + simulator author mode) or
+hand-edit the annotation track for now (spec §4). The ring + manifest entry already
+exist; `process_clip` only replaces the media bytes.