Add mdBook documentation with Ghostty-style sidebar

Dockerfile

@@ -2,7 +2,39 @@
 # This reduces the final image size significantly by separating build and runtime
 
 # ============================================================================
-# Stage 1: Rust Builder
+# Stage 1: Documentation Builder
+# ============================================================================
+FROM rust:1.91-slim-bookworm AS docs-builder
+
+WORKDIR /build
+
+# Install required tools
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends curl ca-certificates && \
+    rm -rf /var/lib/apt/lists/*
+
+# Install mdbook first
+RUN cargo install mdbook
+
+# Copy documentation source (includes theme files)
+COPY docs ./docs
+
+# Download Catppuccin theme CSS if not already present
+RUN if [ ! -f docs/theme/catppuccin.css ]; then \
+    curl -fsSL https://github.com/catppuccin/mdBook/releases/latest/download/catppuccin.css \
+    -o docs/theme/catppuccin.css && \
+    echo "Catppuccin CSS downloaded successfully"; \
+    else \
+    echo "Catppuccin CSS already present"; \
+    fi
+
+# Build documentation
+RUN cd docs && \
+    mdbook build && \
+    ls -la book/
+
+# ============================================================================
+# Stage 2: Rust Builder
 # ============================================================================
 FROM rust:1.91-slim-bookworm AS rust-builder
 
@@ -29,6 +61,14 @@ RUN mkdir src && \
 COPY src ./src
 COPY templates ./templates
 COPY static ./static
+COPY build.rs ./build.rs
+
+# Copy built documentation from docs-builder stage
+COPY --from=docs-builder /build/docs/book ./static/docs
+
+# Verify documentation was copied
+RUN ls -la ./static/docs/ && \
+    test -f ./static/docs/index.html || (echo "ERROR: Documentation index.html not found!" && exit 1)
 
 # Build the actual application (force rebuild by touching sources)
 RUN touch src/server.rs src/lib.rs && \
@@ -36,7 +76,7 @@ RUN touch src/server.rs src/lib.rs && \
     strip target/release/webterm-server
 
 # ============================================================================
-# Stage 2: Node.js Builder
+# Stage 3: Node.js Builder
 # ============================================================================
 FROM node:20-slim AS node-builder
 
@@ -56,7 +96,7 @@ RUN npm ci --only=production && \
     cp static/favicon.png node_modules/
 
 # ============================================================================
-# Stage 3: Runtime Image
+# Stage 4: Runtime Image
 # ============================================================================
 FROM debian:trixie-slim
 
@@ -104,6 +144,10 @@ COPY --from=rust-builder /build/target/release/webterm-server /usr/local/bin/web
 COPY --from=rust-builder /build/templates ./templates
 COPY --from=rust-builder /build/static ./static
 
+# Verify documentation is present in static/docs
+RUN ls -la ./static/docs/ && \
+    test -f ./static/docs/index.html || echo "WARNING: Documentation not found in static/docs"
+
 # Copy node_modules from node-builder
 COPY --from=node-builder /build/node_modules ./node_modules