docs: update build/devenv docs for thirdparty submodules and auto setup

.agents/skills/build-cadmus-native/SKILL.md

@@ -29,16 +29,7 @@ it when documentation sources change.
 
 ## One-time setup
 
-### 1. Native dependencies (MuPDF + C wrapper)
-
-```bash
-cargo xtask setup-native
-```
-
-This downloads MuPDF sources, applies Cadmus-specific patches, and compiles the
-C wrapper library. It is **required** before any compilation or test run.
-
-### 2. (Optional) Download runtime assets
+### Download runtime assets (optional)
 
 ```bash
 cargo xtask download-assets
@@ -47,6 +38,10 @@ cargo xtask download-assets
 Pulls static assets (fonts, icons, etc.) from the latest GitHub release. Not
 strictly required for compilation, but the emulator and some tests expect them.
 
+Native dependencies (MuPDF, libwebp, and the C wrapper) are now built
+automatically by `build.rs` when you run any Cargo command that compiles
+`cadmus-core`.
+
 ## Daily workflow commands
 
 | Goal                         | Command                                                    |
@@ -84,21 +79,20 @@ need to verify a specific one.
 
 - **`fmt`** — runs `cargo fmt --check` (or `--apply` in CI) across the workspace
 - **`clippy`** — iterates the full feature matrix; use `--features` to narrow it
-- **`test`** — iterates the test feature matrix; native deps are assumed built
-- **`run-emulator`** — ensures `setup-native` has run, then `cargo run -p emulator`
-- **`install-importer`** — ensures `setup-native` has run, then `cargo install --path crates/importer`
+- **`test`** — iterates the test feature matrix
+- **`run-emulator`** — runs `cargo run -p emulator`
+- **`install-importer`** — runs `cargo install --path crates/importer`
 
 ## Common mistakes
 
 | Mistake                                                       | Result                                                        | Fix                                                      |
 | ------------------------------------------------------------- | ------------------------------------------------------------- | -------------------------------------------------------- |
 | Running `cargo check` before `cargo xtask docs --mdbook-only` | `RustEmbed` folder-not-found error                            | Generate the EPUB first                                  |
-| Running `cargo test` before `cargo xtask setup-native`        | Linker errors for missing MuPDF / wrapper                     | Run `setup-native` first                                 |
 | Running bare `cargo clippy` / `cargo test` directly           | May miss feature-gated code or use wrong feature combinations | Prefer `cargo xtask clippy` and `cargo xtask test`       |
 | Running `cargo xtask test` without `--features`               | Runs the full (slow) CI matrix locally                        | Pass `--features default` or the specific combo you need |
 
 ## Platform notes
 
-- **Linux**: `setup-native` builds MuPDF from source; ensure `gcc`, `make`, `cmake`, and standard build tools are installed.
-- **macOS**: `setup-native` builds MuPDF from source; Xcode Command Line Tools must be installed.
-- The `build-kobo` command is **Linux-only** (cross-compiles for ARM); it is not covered here because it runs inside a containerised CI action.
+- **Linux**: Native dependencies are built from source automatically via `build.rs`; ensure `gcc`, `make`, `cmake`, and standard build tools are installed.
+- **macOS**: Native dependencies are built from source automatically via `build.rs`; Xcode Command Line Tools must be installed. Full support including Kobo cross-compilation.
+- The `build-kobo` command cross-compiles for ARM and is available on both Linux and macOS; it runs inside a containerised CI action in the main workflow.

.agents/skills/build-kobo/SKILL.md

@@ -4,43 +4,24 @@ description: Cross-compile Cadmus for Kobo e-reader devices (ARM Linux). Use thi
 ---
 
 Use `cargo xtask build-kobo` to cross-compile Cadmus for Kobo devices.
-This task is **Linux only** — the Linaro ARM toolchain consists of x86_64 Linux
-ELF binaries that cannot run on macOS. Use Docker or a Linux VM on macOS.
+The Linaro ARM toolchain is supported on both Linux and macOS hosts.
 
 ## Basic usage
 
 ```sh
-# Fast mode — downloads pre-built .so files (default)
+# Cross-compile for Kobo
 cargo xtask build-kobo
 
-# Slow mode — builds all thirdparty libraries from source (required for CI)
-cargo xtask build-kobo --slow
-
-# Skip library download entirely (when libs/ already exists)
-cargo xtask build-kobo --skip
-
-# Download thirdparty sources only, without building
-cargo xtask build-kobo --download-only
-
 # Build with specific Cargo feature flags
 cargo xtask build-kobo --features test
 ```
 
-## Build modes
-
-| Mode                 | Flag                     | Description                                             |
-| -------------------- | ------------------------ | ------------------------------------------------------- |
-| Fast (default)       | _(none)_                 | Downloads pre-built `.so` files + MuPDF sources         |
-| Slow                 | `--slow`                 | Builds all thirdparty libraries from source             |
-| Slow + download only | `--slow --download-only` | Downloads all thirdparty sources without building       |
-| Skip                 | `--skip`                 | Assumes `libs/` already exists; skips download entirely |
-
 ## What it does
 
 1. Verifies the Linaro ARM toolchain is available on `PATH`
-2. Downloads or builds thirdparty `.so` libraries into `libs/`
-3. Builds the `mupdf_wrapper` C library for the ARM target
-4. Runs `cargo build --release --target arm-unknown-linux-gnueabihf -p cadmus`
+2. Runs `cargo build --release --target arm-unknown-linux-gnueabihf -p cadmus`
+
+Thirdparty dependencies (zlib, bzip2, libpng, libjpeg, openjpeg, jbig2dec, libwebp, freetype2, harfbuzz, gumbo, djvulibre, mupdf) are tracked as git submodules and built automatically by the `build-deps` crate's build.rs when needed. On a warm cache, no submodule initialisation or C/C++ compilation happens.
 
 ## Output
 
@@ -49,7 +30,6 @@ The compiled binary is written to:
 
 ## Prerequisites
 
-- **Linux only** — exits with a clear error on macOS
+- **Linux or macOS** — cross-compilation is supported on both platforms
 - Linaro ARM toolchain on `PATH`: `arm-linux-gnueabihf-gcc`, `arm-linux-gnueabihf-ar`
-  (provided by the devenv shell on Linux)
-- Run `cargo xtask setup-native` first if MuPDF sources are not yet present
+  (provided by the devenv shell)

build-scripts/mupdf/README.md

@@ -1,8 +1,8 @@
 # MuPDF Patches for Cadmus
 
 This directory contains the upstream MuPDF source tree (currently 1.27.0) plus
-Cadmus-specific patches. The patches are applied by `cargo xtask setup-native`
-and by the Kobo build scripts.
+Cadmus-specific patches. The patches are applied automatically by the
+`build-deps` crate's `build.rs` during compilation.
 
 ## Patch overview
 

devenv.nix

@@ -676,14 +676,9 @@ in
       ];
     };
 
-    # Build mupdf and wrapper for native development
-    "deps:native" = {
-      exec = "cargo xtask setup-native";
-    };
-
     # Build for Kobo with cross-compilation
     "build:kobo" = {
-      exec = "cargo xtask build-kobo --slow";
+      exec = "cargo xtask build-kobo";
       after = [ "docs:build" ];
     };
 
@@ -704,14 +699,9 @@ in
       zola serve --base-url http://localhost
     '';
 
-    # Build mupdf for native development
-    cadmus-setup-native.exec = ''
-      cargo xtask setup-native
-    '';
-
     # Build for Kobo device
     cadmus-build-kobo.exec = ''
-      cargo xtask build-kobo --slow
+      cargo xtask build-kobo
       cargo xtask dist
     '';
 
@@ -766,7 +756,6 @@ in
     echo "Cadmus development environment"
     echo ""
     echo "Available commands:"
-    echo "  cadmus-setup-native   - Build mupdf for native development (run once)"
     echo "  cadmus-docs-build     - Build complete documentation portal"
     echo "  cadmus-docs-serve     - Serve documentation locally (http://localhost:1111)"
     echo "  cargo test            - Run tests (after setup)"
@@ -783,7 +772,6 @@ in
     echo "  cadmus-clippy             - Lint lines changed vs master (reviewdog)"
     echo "  cargo xtask clippy        - Lint across feature matrix"
     echo "  cargo xtask test          - Test across feature matrix"
-    echo "  cargo xtask setup-native  - Build MuPDF for native development"
     echo "  cargo xtask docs          - Build documentation portal"
     echo "  cargo xtask dist          - Assemble Kobo distribution"
     echo "  cargo xtask bundle        - Package KoboRoot.tgz"