feat(content): swap cosmos Orion to a text-free SVS flythrough

Replaces the JPL "Orion: Dust and Death" primary (captioned throughout — we'd
cropped it, losing framing) with STScI's "Flight Through the Orion Nebula"
(visible light, NASA SVS 30957) — a full-frame, text-free flythrough of the same
nebula. Sourced via the content pipeline (trim 10–34s + crossfade-loop → 1080p
master + base); cosmos-orbit / abyss-cosmos transitions regenerated from it.

- build_pool_manifest META: cosmos -> SVS 30957, license CC-BY-class (NASA/ESA/
  STScI), new trim window.
- Remove the now-obsolete decaption_cosmos() crop helper (the new source needs
  no caption removal).
- docs/content-candidate-pool.md: record the source swap; drop the crop note.

269 passed, 2 skipped. New clip verified text-free + full-frame by-eye;
final look to be confirmed by the operator.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/content-candidate-pool.md

@@ -27,25 +27,24 @@ stays non‑commercial**.
 
 | id | clip | source | window (s) | license / credit |
 |----|------|--------|-----------|------------------|
-| `cosmos` | Orion Nebula flythrough | NASA/JPL‑Caltech — https://images.nasa.gov/details/JPL-20221122-SOLSYSf-0001-Orion%20Dust%20and%20Death | ~30–54 | PD (17 U.S.C. §105) |
+| `cosmos` | Orion Nebula flythrough | NASA SVS 30957 — https://svs.gsfc.nasa.gov/30957/ (`orion_vis-1920x1080.mp4`, *Flight Through the Orion Nebula*, visible light) | 10–34 | CC‑BY‑class — credit **NASA, ESA, STScI** |
 
-> ⚠️ **Orion is NOT text-free.** The source is the *annotated* "Orion: Dust and
-> Death" visualization — NASA burns lower-third captions in throughout
-> ("DUST FILAMENT", "BLUE BUBBLE", …), so trimming can't avoid them. We crop past
-> them: `simulator/build_pool_manifest.py:decaption_cosmos()` keeps the top 66% of
-> the frame (16:9 preserved, ~1.5× tighter framing) and re-fits to 1920×1080. Run
-> it ONCE after (re)sourcing the Orion clip, then re-run `generate_media()` so the
-> cosmos-orbit / abyss-cosmos transitions use the cropped base.
+> ℹ️ **Orion source swapped to a text-free clip (2026-06-25).** The original
+> primary was NASA/JPL's *"Orion: Dust and Death"* — an annotated visualization
+> with lower-third captions ("DUST FILAMENT", "BLUE BUBBLE", …) burned in
+> throughout, so trimming couldn't avoid them and a crop lost framing. Replaced
+> with STScI's **Flight Through the Orion Nebula** (visible light, SVS 30957) —
+> a full-frame, text-free flythrough of the same nebula. The earlier crop helper
+> (`decaption_cosmos`) is gone; no caption removal is needed for this source.
 | `cosmos_galaxies` | Flying Through Galaxies | NASA SVS — https://svs.gsfc.nasa.gov/vis/a010000/a014900/a014950/14950_Galaxies_FlyThrough_4k.mp4 | 8–32 | PD |
 | `cosmos_hudf` | Hubble Ultra Deep Field zoom | NASA SVS — https://svs.gsfc.nasa.gov/vis/a030000/a030600/a030687/hudf-b-1920x1080p30.mov | 20–44 | CC‑BY‑class — credit **NASA, ESA, STScI** |
 | `cosmos_xdf` | eXtreme Deep Field flythrough | NASA SVS — https://svs.gsfc.nasa.gov/vis/a030000/a030600/a030681/hxdf_fly-b-1920x1080p30.mov | 2–26 | CC‑BY‑class — credit **NASA, ESA, STScI** |
 
 > ⚠️ **DISCREPANCY to fix next session.** Operator selected cosmos **#1, #3
 > (Orion), #4, #5**. During processing, **#6 Galaxy Traverse was run by mistake
-> instead of #3 Orion**. The Orion clip (#3) lives at
-> `simulator/sample_media/cosmos/base.mp4` (the prior real base), so the pool above
-> is correct — but it carries burned-in captions (see the Orion note above; now
-> cropped out). **`cosmos_traverse` is an UNSELECTED extra on disk — drop it** (or
+> instead of #3 Orion**. The cosmos primary now lives at
+> `simulator/sample_media/cosmos/base.mp4` as the text-free SVS 30957 flythrough
+> (see the Orion note above). **`cosmos_traverse` is an UNSELECTED extra on disk — drop it** (or
 > confirm with operator). The current ring scale id is `cosmos`; when the pool is
 > wired, `cosmos` becomes one pool member.