Unify Iron Coast mission names and cinematic mission previews

mods/iron_coast_mission_6/art/briefing-sd-full-rgb-provenance.json

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+{
+  "purpose": "Full RGB SD briefing for the menu; replaces inherited palette posterization",
+  "source": "briefing_hd.png",
+  "source_sha256": "cb87cd81b6d8e87c0ceb5469d1832879906c9cee48728e2c56459b51d8a07b2a",
+  "old_sd_sha256": "7e6304191345cc1f9cffcd30c075887077cd5f2351eaa75fc8c41b792780cd53",
+  "sd_sha256": "e1e8ca85d0ee8039b97b420e082f278967402038e681c46f1b064da58cd4c8ab",
+  "recipe": "rebuild_briefing_sd.py",
+  "method": "RGB 320x200 Lanczos downsample of unchanged approved HD; no image generation",
+  "scope": "Menu illustration only; gameplay terrain, sprites, missions and audio unchanged"
+}

mods/iron_coast_mission_6/art/rebuild_briefing_sd.py

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+#!/usr/bin/env python3
+"""Refresh only this menu briefing SD image; gameplay artwork is untouched."""
+from pathlib import Path
+import hashlib
+from PIL import Image
+root = Path(__file__).resolve().parent
+source = root / "briefing_hd.png"
+assert hashlib.sha256(source.read_bytes()).hexdigest() == "cb87cd81b6d8e87c0ceb5469d1832879906c9cee48728e2c56459b51d8a07b2a", "Unexpected HD briefing"
+with Image.open(source) as image:
+    image.convert("RGB").resize((320,200), Image.Resampling.LANCZOS).save(root / "briefing_sd.png")