Document and package the new libjpeg-turbo dependency

Tight's JPEG sub-mode (previous commit) links libjpeg-turbo directly.
Adds it to docs/BUILDING.md for all three platforms (apt
libjpeg-turbo8-dev, brew jpeg-turbo, vcpkg libjpeg-turbo:x64-windows)
and to the .deb package's Depends: line (libjpeg-turbo8). No changes
needed for Windows (the Inno Setup script already wildcards *.dll) or
macOS (macdeployqt bundles non-system dylibs automatically). Left the
Flatpak manifests unchanged on the assumption that the KDE runtime
already bundles libjpeg-turbo as a standard Qt JPEG-plugin dependency
-- flagged in PROGRESS.md as worth confirming next time a Flatpak
build actually runs, since that wasn't independently verified here.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/BUILDING.md

@@ -17,7 +17,7 @@ sudo apt update
 sudo apt install -y \
   build-essential cmake ninja-build git pkg-config \
   qt6-base-dev qt6-base-dev-tools qt6-tools-dev qt6-tools-dev-tools \
-  openssh-client libssl-dev zlib1g-dev
+  openssh-client libssl-dev zlib1g-dev libjpeg-turbo8-dev
 
 cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
 cmake --build build
@@ -29,11 +29,11 @@ cmake --build build
 ```bash
 xcode-select --install
 brew update
-brew install cmake ninja pkg-config qt@6 openssh openssl@3
+brew install cmake ninja pkg-config qt@6 openssh openssl@3 jpeg-turbo
 
 cmake -S . -B build -G Ninja \
   -DCMAKE_BUILD_TYPE=Release \
-  -DCMAKE_PREFIX_PATH="$(brew --prefix qt@6);$(brew --prefix openssl@3)"
+  -DCMAKE_PREFIX_PATH="$(brew --prefix qt@6);$(brew --prefix openssl@3);$(brew --prefix jpeg-turbo)"
 cmake --build build
 open build/orbithub.app
 ```
@@ -56,7 +56,7 @@ Install dependencies via vcpkg:
 ```powershell
 git clone https://github.com/microsoft/vcpkg C:\dev\vcpkg
 C:\dev\vcpkg\bootstrap-vcpkg.bat
-C:\dev\vcpkg\vcpkg.exe install qtbase:x64-windows openssl:x64-windows zlib:x64-windows
+C:\dev\vcpkg\vcpkg.exe install qtbase:x64-windows openssl:x64-windows zlib:x64-windows libjpeg-turbo:x64-windows
 ```
 
 Open `x64 Native Tools Command Prompt for VS 2022` (or Developer PowerShell), then build:
@@ -75,7 +75,7 @@ Run (ensures DLL paths from vcpkg are present):
 C:\dev\vcpkg\vcpkg.exe env --triplet x64-windows -- .\build\orbithub.exe
 ```
 
-If you already have `Qt 6` from the Qt installer and do not want vcpkg Qt, you can point CMake at that Qt install with `-DCMAKE_PREFIX_PATH=...`, but you still need compatible `OpenSSL` and `zlib` development libraries for the embedded FreeRDP build.
+If you already have `Qt 6` from the Qt installer and do not want vcpkg Qt, you can point CMake at that Qt install with `-DCMAKE_PREFIX_PATH=...`, but you still need compatible `OpenSSL`, `zlib`, and `libjpeg-turbo` development libraries (the first two for the embedded FreeRDP build; `libjpeg-turbo` for VNC's Tight encoding's JPEG sub-mode).
 
 ## Notes
 

docs/PROGRESS.md

@@ -199,6 +199,16 @@ follow-up tracking):
   is the least exercised/confirmed of the three filters against a real
   server in this pass (most real-world Tight traffic uses Copy or
   Palette)
+- Packaging for the new `libjpeg-turbo` dependency: added to
+  `docs/BUILDING.md` (apt/brew/vcpkg) and the `.deb` control file's
+  `Depends:` (`libjpeg-turbo8`). The Windows Inno Setup script already
+  wildcards `*.dll` so no change was needed there, and macOS's
+  `macdeployqt`-based bundling picks up non-system dylibs automatically.
+  The Flatpak manifests (`packaging/flatpak/*.yml`) were left unchanged on
+  the assumption that `org.kde.Platform`/`Sdk` 6.11 already bundles
+  libjpeg-turbo (a standard Qt JPEG-plugin dependency) -- worth confirming
+  the next time a Flatpak build is actually run, since it wasn't
+  independently verified here
 - No dynamic resize (connects at the server's native resolution; the
   `Scale to Fit`/`Actual Size` toggle changes how that fixed resolution is
   displayed locally, not what resolution is requested from the guest --