Extract volrover3 application to the volrover repository

[transfix]

What moved

Executes goal G4 (near-term-goals-2026-07-15): libcvc becomes a lean SDK (library + cvc CLI); the VolumeRover3 application now lives in transfix/volrover.

Removed from this repo:

• src/volrover3/ (45 files: sources, tests, CMakeLists, README) and inc/volrover3/ (28 headers)
• share/ (volrover3.desktop.in + volrover_logo icons), CMake/Info.plist.in (only used by the volrover3 macOS bundle), build_volrover3.sh
• docs/GRAPHICS_SYSTEM.md, docs/GRAPHICS_DATA_DRIVEN_UPDATES.md, docs/APPSTATE_CALLBACKS.md — these document volrover3 app classes (SceneGraph/GraphicsNode/AppState) and move with the app. Docs describing libcvc core (APP_API, STATE_API, CLI_GUIDE, TESTING, etc.) stay.
• CVC_BUILD_VOLROVER3 option + Qt/VTK detection in src/CMakeLists.txt
• volrover3 CPack component, DEB/NSIS app packaging, and icon install rules in the top-level CMakeLists.txt. CMAKE_INSTALL_SYSTEM_RUNTIME_COMPONENT now targets libcvc so MSVC CRT/OpenMP runtimes still ship with the Windows SDK zip. Windows default CPACK_GENERATOR drops NSIS (that was the app installer).
• CI: volrover3 matrix entries and all volrover3-gated steps in ci.yml and release.yml (AppImage/deb/dmg/NSIS packaging, VTK-from-source builds and caches, aqtinstall Qt6, DLL verification). .github/scripts/verify-windows-deps.ps1 moved to the volrover repo. nightly.yml comment updated.

One SDK fix that fell out of verification (second commit): cvc/utility/utility.h unconditionally includes <xmlrpc/XmlRpc.h>, but inc/xmlrpc/ headers were only installed when CVC_USING_XMLRPC=ON — external find_package(cvc) consumers that include cvc/utility/algorithm.h (as volrover3 does) could not compile against an XMLRPC-off SDK. The vendored XmlRpc++ headers now always install with the libcvc component.

History decision (flagged for review)

The app was imported into transfix/volrover as a plain copy with a provenance note (source commit 03b4f961f834c46fcd19b9b4b633dc4c1c8bdcfc recorded in the import commit message) — no git-filter-repo history rewrite. Full file history remains reachable here. Object if you want the history carried over instead.

Verification

• cmake configure passes with volrover3 removed (Release, Ninja, local cvcpkg deps prefix for Boost 1.86/CGAL/ImageMagick/FFTW/GSL/libiimod, CUDA off)
• libcvc.so (152 targets) and the cvc CLI build clean from the branch
• The moved app was verified in the volrover PR: configure + full build of volrover3 against the packaged libcvc SDK (dist-cvcpkg 3.2.4+cvc.1 tarball + the xmlrpc-headers fix), and all 14 volrover3 unit tests pass (QT_QPA_PLATFORM=offscreen)
• Not verified here: macOS/Windows CI paths of the trimmed workflows (YAML validated; the removed steps were all gated on matrix.kind == 'volrover3')

Notes for review

• cvc-requirements.yaml still lists qt6 and vtk; they were only needed by volrover3 and can likely be dropped in a follow-up (left untouched to avoid colliding with the in-flight cvcpkg recipe branch).
• This branch will conflict with feat/libcvc-cvcpkg-recipe-and-release-publish in .github/workflows/ (that branch also rewrites ci.yml/release.yml); whichever lands second needs a rebase.

Counterpart PR in volrover: transfix/volrover#13

[transfix]

Rebased onto master at 30e079d (post-#101 merge) and force-pushed; the branch is now the same two commits replayed on top of the cvcpkg recipe / release-publish machinery.

What was re-resolved (conflicts were confined to .github/workflows/ci.yml and release.yml):

• Took master's Add libcvc cvcpkg recipe and enable release-time cvcpkg publish #101 versions of both workflows as the base — the cvcpkg-based dependency flow (fetch-libcvc-deps via cvcpkg-install, cvc-requirements.yaml) and publish-cvcpkg.yml are fully preserved — then re-applied the volrover3 strip to them: removed the volrover3 matrix entries, the volrover3 dependency-install steps, -DCVC_BUILD_VOLROVER3 configure flags, AppImage/.deb/dmg/NSIS packaging, the Windows DLL-verification steps, volrover3 artifact uploads, and the volrover3 release-asset globs in the release job.
• New in this rebase (these files came from Add libcvc cvcpkg recipe and enable release-time cvcpkg publish #101 and did not exist on the old base): dropped the volrover3-only qt6 and vtk entries from cvc-requirements.yaml and from cvcpkg/recipes/libcvc/recipe.yaml's runtime depends, and removed -DCVC_BUILD_VOLROVER3=OFF from the recipe's build.sh / build.ps1. The recipe now packages the SDK + cvc CLI only; the xmlrpc-headers commit additionally lists include/xmlrpc/ in the recipe's package.files so packaged SDK artifacts ship the headers the installed cvc/utility/utility.h needs.
• Also caught in this pass: removed test_threading_behavior.cpp (an unwired root-level scratch program with its own main() that includes <volrover3/...> headers and cannot compile here after the extraction). It is preserved in Carry over test_threading_behavior.cpp scratch program from libcvc volrover#14 under volrover3/tests/manual/.

Verification on the rebased branch (Linux, Release/Ninja, CUDA off, local cvcpkg deps prefix): fresh configure passes; full build of libcvc.so and the cvc CLI succeeds (154/154 targets); cmake --install --component libcvc confirmed to stage include/cvc and include/xmlrpc. All six workflow/recipe YAMLs parse cleanly. macOS/Windows workflow paths not executed locally — PR CI will exercise the trimmed matrices.

Not merging per instructions — ready for review.

[transfix]

CI status note: the rebased branch's run fails every package job at the "Fetch libcvc-deps" step. This is pre-existing breakage, not from this PR — master's own CI run on the #101 merge commit (run 29461865764 on 30e079d) fails at the exact same step in all package jobs. The failure is inside the upstream transfix/libcvc-deps cvcpkg-install action: pip metadata generation for the cvcpkg tool aborts with "Readme path .../_libcvc-deps/README.md does not exist", so it needs a fix in the libcvc-deps repo (the action's checkout is missing the README.md its pyproject references).

Signal that IS attributable to this PR: clang-format passes, and the volrover3 jobs are gone from the matrices as intended (this PR's run has only libcvc-* package jobs).