fix: restore booklet viewer with mupdf 0.6 (#170)

mupdf 0.5 had struct size mismatches on Arch Linux (mupdf-sys bindings
incompatible with system MuPDF headers). Upgrading to mupdf 0.6 fixes
the bindings.

- Removed the booklet feature gate — mupdf is now a direct dependency
  again, matching the v1.1.19 configuration
- Removed stub implementation (always compile real MuPDF backend)
- sys-lib-libjpeg remains excluded (cross-distro libjpeg incompatibility)

cc

src-tauri/Cargo.toml

@@ -13,10 +13,6 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 name = "qbz"
 path = "src/main.rs"
 
-[features]
-default = []
-booklet = ["mupdf"]
-
 [build-dependencies]
 tauri-build = { version = "2", features = [] }
 
@@ -107,7 +103,7 @@ image = { version = "0.25", default-features = false, features = ["png", "jpeg",
 # GTK/GdkPixbuf. But NOT libjpeg — Ubuntu ships libjpeg8 (libjpeg.so.8) while
 # Debian/Fedora ship libjpeg62-turbo (libjpeg.so.62). Let mupdf vendor its own
 # libjpeg to avoid cross-distro breakage (GitHub #161, #162).
-mupdf = { version = "0.5", default-features = false, optional = true, features = [
+mupdf = { version = "0.6", default-features = false, features = [
   "system-fonts",
   "sys-lib-zlib",
   "sys-lib-harfbuzz",

src-tauri/src/pdf_viewer.rs

@@ -53,10 +53,9 @@ fn booklet_temp_dir() -> PathBuf {
 }
 
 // ---------------------------------------------------------------------------
-// Real MuPDF implementation (feature = "booklet")
+// MuPDF implementation
 // ---------------------------------------------------------------------------
 
-#[cfg(feature = "booklet")]
 mod real_impl {
     use super::*;
     use base64::Engine;
@@ -264,52 +263,10 @@ mod real_impl {
 }
 
 // ---------------------------------------------------------------------------
-// Stub implementation (no MuPDF)
+// Public Tauri commands — delegate to MuPDF implementation
 // ---------------------------------------------------------------------------
 
-#[cfg(not(feature = "booklet"))]
-mod stub_impl {
-    use super::*;
-
-    const UNAVAILABLE: &str =
-        "Booklet viewer unavailable: built without MuPDF (enable the 'booklet' feature)";
-
-    pub async fn open(
-        _url: String,
-        _state: &tauri::State<'_, BookletState>,
-    ) -> Result<BookletInfo, String> {
-        Err(UNAVAILABLE.to_string())
-    }
-
-    pub async fn render_page(
-        _page: u32,
-        _dpi: u32,
-        _rotation: Option<u32>,
-        _state: &tauri::State<'_, BookletState>,
-    ) -> Result<RenderedPage, String> {
-        Err(UNAVAILABLE.to_string())
-    }
-
-    pub async fn save(
-        _dest: String,
-        _state: &tauri::State<'_, BookletState>,
-    ) -> Result<(), String> {
-        Err(UNAVAILABLE.to_string())
-    }
-
-    pub async fn close(_state: &tauri::State<'_, BookletState>) -> Result<(), String> {
-        Err(UNAVAILABLE.to_string())
-    }
-}
-
-// ---------------------------------------------------------------------------
-// Public Tauri commands — delegate to the active implementation
-// ---------------------------------------------------------------------------
-
-#[cfg(feature = "booklet")]
 use real_impl as impl_;
-#[cfg(not(feature = "booklet"))]
-use stub_impl as impl_;
 
 /// Download a PDF from a URL, save to temp, and return page info.
 #[tauri::command]