fix(rivetkit): build:browser depends on upstream builds

The dependsOn was stripped in fa64439 when build:schema (which
transitively provided ^build) was removed. Without it, tsup DTS races
against @rivetkit/virtual-websocket#build and can't resolve types.

Author: NathanFlurry

rivetkit-typescript/packages/rivetkit/turbo.json

@@ -46,6 +46,7 @@
 			"env": ["FAST_BUILD", "CUSTOM_RIVETKIT_DEVTOOLS_URL"]
 		},
 		"build:browser": {
+			"dependsOn": ["^build"],
 			"inputs": [
 				"src/client/mod.browser.ts",
 				"src/**",