docs: set rustdoc default theme to dark

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: GiggleLiu

.github/workflows/docs.yml

@@ -46,7 +46,7 @@ jobs:
         run: make examples && typst compile docs/paper/reductions.typ book/reductions.pdf
 
       - name: Build rustdoc
-        run: cargo doc --all-features --no-deps
+        run: RUSTDOCFLAGS="--default-theme=dark" cargo doc --all-features --no-deps
 
       - name: Combine documentation
         run: |

Makefile

@@ -48,15 +48,15 @@ doc:
 	cargo run --example export_graph
 	cp docs/paper/reduction_graph.json docs/src/reductions/
 	mdbook build docs
-	cargo doc --all-features --no-deps
+	RUSTDOCFLAGS="--default-theme=dark" cargo doc --all-features --no-deps
 	rm -rf docs/book/api
 	cp -r target/doc docs/book/api
 
 # Build and serve mdBook with API docs
 mdbook:
 	cargo run --example export_graph
 	cp docs/paper/reduction_graph.json docs/src/reductions/
-	cargo doc --all-features --no-deps
+	RUSTDOCFLAGS="--default-theme=dark" cargo doc --all-features --no-deps
 	mdbook build
 	rm -rf book/api
 	cp -r target/doc book/api