Phase 9: Iris and Complementary Reimagined, off by default

Adrian, 2026-11-09: set up the shader but keep it disabled by default. Iris
1.8.14-beta.1 (built for the pack's Sodium 0.8.13) and Complementary Reimagined
r5.9.3, both client only and fetched from Modrinth. Default Options' extra
folder ships config/iris.properties with shaders off and Complementary
preselected, copied only when a player has none. Toggle Shaders is on M, the
only free letter; Iris's other keys are unbound. tools/build.py fails if the
settings name a shader file the pack doesn't install.

Smoke test passes; client dependencies are satisfied. Not launched on a client.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pack/config/defaultoptions/keybindings.txt

@@ -38,3 +38,6 @@ key_key.ftbquests.gui_quest_panel.edit_quest_props:key.keyboard.unknown
 key_key.ftbquests.gui_quest_panel.edit_subtitle:key.keyboard.unknown
 key_key.ftbquests.gui_quest_panel.edit_title:key.keyboard.unknown
 key_key.ftbquests.gui_quest_panel.add_image:key.keyboard.unknown
+key_iris.keybind.toggleShaders:key.keyboard.m
+key_iris.keybind.reload:key.keyboard.unknown
+key_iris.keybind.shaderPackSelection:key.keyboard.unknown