FileAssoc: Slice E — Verification matrix, automated tests, install-time UX, marketing

[fernandotonon]

Parent epic: #664
Depends on: Slices A–D (#665, #666, #667, #668).

Goal

Close out the epic with the verification, install-time UX, and discoverability work that turns "the app can open files" into "the app gets used to open files".

Scope

Verification matrix in CI

A new GitHub Actions job per OS that:

• macOS: builds the bundle, drops it into /Applications, runs lsregister -f, then runs macos/verify-file-association.sh (from Slice B) against a fixture file. Fail the build if registration is missing.
• Windows: installs the Inno Setup installer (silent mode), runs scripts/verify-windows-association.ps1 (from Slice C) against fixture files. Uninstalls and verifies clean uninstall.
• Linux: installs the .deb on a clean Ubuntu container, runs scripts/verify-linux-association.sh (from Slice D), then uninstalls and verifies clean removal.

These run on every release build (not every PR — too slow / VM-heavy). The existing release pipeline at .github/workflows/deploy.yml is the right place.

Install-time UX

• macOS: After the user drops QtMeshEditor.app into Applications and runs it the first time, show a one-time "Make QtMeshEditor the default app for 3D model files?" dialog. If the user clicks "Yes", call the macOS Launch Services API (LSSetDefaultRoleHandlerForContentType) to set QtMeshEditor as default for the QtMeshEditor-native UTIs (.mesh, .rsd, .tmd, .material). For non-native formats (.fbx, etc.) explain that the user controls those via Finder's Get Info → Open With → Change All UI.
• Windows: Slice C already plans the first-launch prompt that deep-links to ms-settings:defaultapps. Slice E ensures it's actually implemented.
• Linux: After install, the existing mainwindow.cpp-side "first launch" path checks xdg-mime query default model/gltf-binary and, if it's not QtMeshEditor, shows a banner with a "Set as default" button that calls xdg-mime default qtmesheditor.desktop model/gltf-binary (one call per supported type).
• All three prompts have a "Don't ask again" checkbox stored in QSettings.

Recently-opened files

• A "Recent Files" menu entry under File that tracks the last 10 files opened (regardless of source — argv, FileOpenEvent, drag-and-drop from desktop, or menu pick).
• Persisted in QSettings. Implemented in MainWindow.
• Surfaces in the macOS Dock's right-click → Recent Files automatically (macOS reads recent docs from a per-app NSDocumentController; we plumb that with [[NSDocumentController sharedDocumentController] noteNewRecentDocumentURL:]).
• Windows: Jump List integration (SetCurrentProcessExplicitAppUserModelID + ICustomDestinationList). Use the Qt Windows extras if available; otherwise WinAPI direct.

Drag-and-drop into the running app

• MainWindow accepts QDragEnterEvent / QDropEvent on the viewport. Dropping a file from Finder/Explorer/Nautilus loads it (or asks user "Open as new entity?" vs "Merge into current scene?" for non-first drops).
• Already partial in the existing code? Verify and complete.

Marketing / discoverability

Not code, but ships with this epic:

• README hero update: lead with "Free 3D model viewer — opens FBX, glTF, OBJ, DAE, STL and 5+ more formats with one click. macOS, Windows, Linux." Move the technical detail (Ogre, Qt, CLI) below the fold.
• Website (website/) mirror update.
• Changelog entry: "QtMeshEditor is now your default 3D model viewer. Install it once, then double-click any .fbx, .glb, .obj, or other supported model from your file manager — it just opens."
• Reddit / forum posts: write a one-page draft pitching QtMeshEditor as "the missing Preview.app for 3D models" — to be posted by the maintainer to r/gamedev, r/blender, r/IndieDev around the time the release ships. (Out of scope for the code PR; included in the issue checklist as a release-day task.)
• Sketchfab / Poly Haven / Mixamo SEO: a short blog post titled "How to open .fbx / .glb files without installing Blender" that points to QtMeshEditor. SEO landing page lives on the website. Drives the long-tail search traffic.
• Submit to:
  • AlternativeTo.com — list QtMeshEditor as an alternative to "Microsoft 3D Viewer" (discontinued), "Apple Preview" (limited), Blender (heavy), various paid viewers.
  • Slant.co — submit under "Best free 3D model viewer".
  • GitHub topic tags: add 3d-model-viewer, fbx-viewer, gltf-viewer, obj-viewer, default-app to the repo topics.

Documentation

• New "File Associations" section in CLAUDE.md documenting:
  • Which formats are registered on which OS.
  • How to verify registration.
  • How to unregister / change defaults.
  • The CLI fallback (qtmesh ... always wins).

Acceptance Criteria

• CI's verification matrix runs on every release build and blocks the build if registration is missing on any of the three OSes.
• First-launch default-app prompt fires once on each OS with persistent "Don't ask again".
• Recent Files menu populated correctly.
• macOS Dock right-click shows Recent Documents.
• Windows Jump List shows Recent Documents.
• Drag-and-drop a file from desktop to the viewport loads it.
• README + website + changelog updated.
• AlternativeTo / Slant submissions filed (link in the PR description).
• CLAUDE.md File Associations section landed.

Effort

~6 days for the code (verification + UX + recents); marketing is separate cycle time.