Summary

• Retry desktop tab startup when a saved session lease is still held by another Reasonix process and later becomes available.
• Reuse the deferred rebuild loop for startup lease recovery and kick it when the app window is shown again.
• Retry synchronously before tab actions so send and terminal paths can recover instead of leaving a stale startup error banner.

Tests

• cd desktop && go test -run 'TestBuildTabControllerBlocksWhenSessionLeaseHeld|TestDeferredStartupRetryBuildsAfterLeaseRelease|TestTabAndCtrlByIDRecoversStartupLeaseBeforeAction|TestDeferredRebuildRetryAppliesAfterLeaseRelease|TestDeferredRebuildWaitsForTabToBecomeActive|TestConfigChangeLeaseHeldPersistsAndDefersRefresh|LeaseHeld|RecoveryFailed' .\n- cd desktop && go test -short .\n- go test ./internal/agent\n- git diff --check\n- cd desktop && wails build