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/mods/iris.pw.toml

@@ -0,0 +1,13 @@
+name = "Iris Shaders"
+filename = "iris-neoforge-1.8.14-beta.1+mc1.21.1.jar"
+side = "client"
+
+[download]
+url = "https://cdn.modrinth.com/data/YL57xq9U/versions/KduFYu4t/iris-neoforge-1.8.14-beta.1%2Bmc1.21.1.jar"
+hash-format = "sha512"
+hash = "33fddb430e16222902eac75b8b3d57c381b0f3cc729f3b56c4628df12ca108f23a0b11e2feb167923d6d14d1fc7e8ee1a977ec421b19d1951bdca74c4092b9c5"
+
+[update]
+[update.modrinth]
+mod-id = "YL57xq9U"
+version = "KduFYu4t"