ifcviewer: preset-driven nav mouse bindings + a "Web" preset (desktop + web)

Make orbit/pan/select mouse bindings pure data owned by ViewportCore so both
hosts and every preset share one source of truth, and add a "Web" preset. This
rounds out the matrix: the desktop gains a web-style scheme and the web inherits
all presets, with no per-platform hardcoding.

- Core: NavBindings { orbit, pan, select button + modifier } + setNavPreset
  ("blender" default | "rhino" | "revit" | "web") + navBindings(). Select is
  preset-driven too (was hardcoded LMB) so "web" moves it to RMB. web = orbit
  LMB, pan MMB, select RMB (LMB drag orbits with no click/drag ambiguity; RMB
  click-selects / drag-marquees). NavMod uses "Plain" not "None" (X11 #defines
  None to 0L).
- Desktop ViewportWindow: applyNavPreset sources the core table (mapped to Qt);
  marquee-arm / single-pick dispatch keys off select_button_. Default stays
  blender → no behaviour change.
- Desktop config: AppSettings::NavPreset gains Web + navPresetName(); the
  Settings dialog lists it. This also FIXES a pre-existing gap — the preset combo
  was persisted but never applied (only WGPU_NAV_PRESET env worked). MainWindow
  now applies the persisted preset at startup (env override still wins) and live
  on navPresetChanged, so all four presets actually work from the dialog.
- Web main_web: classifyPress routes the pressed button through navBindings()
  (orbit/pan/select), defaulting to the "web" preset; context menu already
  suppressed so RMB is free.

Tests: setNavPreset table (Catch2, 123 total); web smoke select tests use RMB.
BonsaiViewer builds; 9/9 web smoke.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ifcviewer/ViewportCore.h

@@ -192,6 +192,30 @@ public:
     enum class StandardView { Front, Back, Left, Right, Top, Bottom };
     void setStandardView(StandardView view);
 
+    // ---- Navigation mouse bindings (shared, preset-driven) ------------------
+    //
+    // Which mouse button (+ modifier) orbits / pans / selects. Owned by the core
+    // as pure data so BOTH hosts and ALL presets share one source of truth — the
+    // desktop maps these to Qt::MouseButton, the web to DOM button codes. Select
+    // is preset-driven too (not hardcoded to LMB) so a "web" preset can move it
+    // to RMB. Marquee box-select uses the same button as select (drag vs click).
+    enum class MouseBtn { Left, Middle, Right };
+    // Plain (not "None": X11 #defines None to 0L, which would corrupt the token).
+    enum class NavMod   { Plain, Shift, Ctrl, Alt };
+    struct NavBindings {
+        MouseBtn orbit;  NavMod orbit_mod;
+        MouseBtn pan;    NavMod pan_mod;
+        MouseBtn select; NavMod select_mod;
+    };
+    // name: "blender" (default) | "rhino" | "revit" | "web". Unknown → blender.
+    //   blender  orbit MMB,        pan Shift+MMB,  select LMB
+    //   rhino    orbit RMB,        pan Shift+RMB,  select LMB
+    //   revit    orbit Shift+MMB,  pan MMB,        select LMB
+    //   web      orbit LMB,        pan MMB,        select RMB (LMB stays free to
+    //            orbit-drag; RMB click-selects / drag-marquees, no ambiguity)
+    void setNavPreset(const char* name);
+    const NavBindings& navBindings() const { return nav_bindings_; }
+
     // Frame the current selection: union the selected objects' world AABBs and
     // fit the camera to them (same 1.30 padding as the desktop "F" hotkey).
     // No-op with an empty selection or no resolvable AABBs; returns whether it
@@ -1151,6 +1175,10 @@ private:
     // Fly-camera move speed (m/s), wheel-adjustable via flyAdjustSpeed. Shared
     // by desktop + web fly mode; the mode flag itself lives in each host.
     float fly_move_speed_    = 5.0f;
+    // Nav mouse bindings; default matches the historical "blender" preset.
+    NavBindings nav_bindings_ = { MouseBtn::Middle, NavMod::Plain,
+                                  MouseBtn::Middle, NavMod::Shift,
+                                  MouseBtn::Left,   NavMod::Plain };
     // Perspective by default; toggleProjection (P key) flips this. When
     // true, buildViewProj uses an orthographic matrix sized by
     // camera_distance_ × tan(fov/2) so toggling looks like a smooth