Add a Steam Frame build option; no chaperone commit at start; timer-based tick

- CMake option OVRAS_STEAM_FRAME. It is evaluated only in
  src/utils/platform_capabilities.h, which turns it into named capability
  constants and platform defaults.
- Where the chaperone can't be committed (Steam Frame: it shifts the play
  area), MoveCenterTabController no longer commits the working copy at start-up
  or when applying reset data, and doesn't create the init autosave profile.
  Skips are logged once.
- In "vsync disabled" mode the pump timer now runs directly at the custom tick
  rate instead of firing every 1 ms and counting. The Frame defaults to this
  mode at 11 ms (~90 Hz).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/tabcontrollers/MoveCenterTabController.cpp

@@ -1,10 +1,13 @@
 #include "MoveCenterTabController.h"
 #include <QQuickWindow>
+#include <set>
+#include <string>
 #include <QtLogging>
 #include <QtDebug>
 #include "../overlaycontroller.h"
 #include "../quaternion/quaternion.h"
 #include "../settings/settings.h"
+#include "../utils/platform_capabilities.h"
 
 void rotateCoordinates( double coordinates[3], double angle )
 {
@@ -1106,7 +1109,13 @@ void MoveCenterTabController::zeroOffsets()
                 if ( calState != 200 )
                 {
                     // all init complete, safe to autosave chaperone profile
-                    parent->m_chaperoneTabController.createNewAutosaveProfile();
+                    // Not where the chaperone can't be committed: the autosave
+                    // exists to restore a committed play area later.
+                    if ( platform::k_chaperoneCommitSupported )
+                    {
+                        parent->m_chaperoneTabController
+                            .createNewAutosaveProfile();
+                    }
                     m_initComplete = true;
                     m_chaperoneBasisAcquired = true;
                     qInfo() << "Chaperone Initilization Complete, Space Drag "
@@ -1172,6 +1181,19 @@ void MoveCenterTabController::clampVelocity( double* velocity )
     }
 }
 
+// Logs once per caller that a chaperone commit was skipped, so the log shows
+// it without repeating it every tick.
+static void logSkippedChaperoneCommit( const char* caller )
+{
+    static std::set<std::string> logged;
+    if ( logged.insert( caller ).second )
+    {
+        qInfo() << caller
+                << ": CommitWorkingCopy skipped, not supported on this "
+                   "platform (logged once)";
+    }
+}
+
 void MoveCenterTabController::updateChaperoneResetData()
 {
     //auto cstate = vr::VRChaperone()->GetCalibrationState();
@@ -1183,9 +1205,20 @@ void MoveCenterTabController::updateChaperoneResetData()
     // }
     // else
     //{
+
+    // Committing writes the working copy as the live play area. Where that
+    // isn't supported (it shifts the play area on the Steam Frame), only the
+    // working copy is read below.
+    if ( platform::k_chaperoneCommitSupported )
+    {
         vr::VRChaperoneSetup()->CommitWorkingCopy(
             vr::EChaperoneConfigFile_Live );
         vr::VRChaperoneSetup()->RevertWorkingCopy();
+    }
+    else
+    {
+        logSkippedChaperoneCommit( "updateChaperoneResetData" );
+    }
     //}
     unsigned currentQuadCount = 0;
     vr::VRChaperoneSetup()->GetWorkingCollisionBoundsInfo( nullptr,
@@ -1228,7 +1261,16 @@ void MoveCenterTabController::applyChaperoneResetData()
     //  vr::VRChaperoneSetup()->SetWorkingSeatedZeroPoseToRawTrackingPose(
     //     &m_seatedCenterForReset );
 
-    vr::VRChaperoneSetup()->CommitWorkingCopy( vr::EChaperoneConfigFile_Live );
+    // See updateChaperoneResetData(): no commit where it isn't supported.
+    if ( platform::k_chaperoneCommitSupported )
+    {
+        vr::VRChaperoneSetup()->CommitWorkingCopy(
+            vr::EChaperoneConfigFile_Live );
+    }
+    else
+    {
+        logSkippedChaperoneCommit( "applyChaperoneResetData" );
+    }
 
     unsigned checkQuadCount = 0;
     vr::VRChaperoneSetup()->GetWorkingCollisionBoundsInfo( nullptr,