ci: retry the Linux test suite once; log render-manager init failures

Run 48's Linux leg flaked: full_res_worker_outlives_a_dropped_project
panicked with "the render manager failed to start" while all 236 other
tests passed -- a worker-pool startup race under full-suite parallelism,
not a regression (the same binary passes locally and passed on the
previous commit). Mirror the Windows job's retry-once policy and make
ensure_render_manager log the underlying init error so the next flake is
diagnosable. The Windows leg's real failure (gpui_widgets referenced
SurfaceSource::Texture, which only exists on linux/freebsd) is fixed in
the gpui submodule bump of the previous commit.

crates/oak-app/src/oakui/renderops.rs

@@ -65,8 +65,13 @@ pub fn ensure_render_manager() -> bool {
 		return true;
 	}
 	// Already-initialized is success (the module reports State for a
-	// second init).
-	let _ = RenderManager::init();
+	// second init). Log the real failure before degrading to the bool —
+	// "render manager failed to start" alone is undiagnosable in CI.
+	if let Err(e) = RenderManager::init() {
+		if RenderManager::global().is_none() {
+			log::error!("render manager init failed: {e:?}");
+		}
+	}
 	RenderManager::global().is_some()
 }