refactor(core): replace sync event cast with Schema guard

Use Schema.is to narrow converted sync events instead of asserting the payload type manually. Move the Zod-to-Effect bridge into effect-zod so remaining Zod-backed sync payloads have one explicit interop helper.

packages/opencode/src/server/projectors.ts

@@ -5,12 +5,14 @@ import { Session } from "@/session"
 import { SessionTable } from "@/session/session.sql"
 import { Database, eq } from "@/storage"
 
+const isSessionUpdated = Schema.is(Session.Event.Updated.schema)
+
 export function initProjectors() {
   SyncEvent.init({
     projectors: sessionProjectors,
     convertEvent: (type, data) => {
-      if (type === "session.updated") {
-        const id = (data as Schema.Schema.Type<typeof Session.Event.Updated.schema>).sessionID
+      if (type === Session.Event.Updated.type && isSessionUpdated(data)) {
+        const id = data.sessionID
         const row = Database.use((db) => db.select().from(SessionTable).where(eq(SessionTable.id, id)).get())
 
         if (!row) return data

packages/opencode/src/session/session.ts

@@ -28,7 +28,7 @@ import type { Provider } from "@/provider"
 import { Permission } from "@/permission"
 import { Global } from "@/global"
 import { Effect, Layer, Option, Context, Schema, Types } from "effect"
-import { ZodOverride, zod, zodObject } from "@/util/effect-zod"
+import { fromZod, zod, zodObject } from "@/util/effect-zod"
 import { withStatics } from "@/util/schema"
 
 const log = Log.create({ service: "session" })
@@ -215,13 +215,7 @@ export const MessagesInput = Schema.Struct({
   limit: Schema.optional(Schema.Number),
 }).pipe(withStatics((s) => ({ zod: zod(s) })))
 
-function schemaFromZod<T extends z.ZodTypeAny>(value: T) {
-  return Schema.declare((input): input is z.output<T> => value.safeParse(input).success).annotate({
-    [ZodOverride]: value,
-  })
-}
-
-const SessionUpdateInfoSchema = schemaFromZod(
+const SessionUpdateInfoSchema = fromZod(
   updateSchema(zodObject(Info)).extend({
     share: updateSchema(zodObject(Share)).optional(),
     time: updateSchema(zodObject(Time)).optional(),

packages/opencode/src/util/effect-zod.ts

@@ -49,6 +49,14 @@ function isZodType(value: unknown): value is z.ZodTypeAny {
   return typeof value === "object" && value !== null && "_zod" in value
 }
 
+// Bridge a Zod-first schema into Effect Schema while preserving the original
+// Zod for downstream JSON Schema/OpenAPI generation.
+export function fromZod<T extends z.ZodTypeAny>(value: T) {
+  return Schema.declare((input): input is z.output<T> => value.safeParse(input).success).annotate({
+    [ZodOverride]: value,
+  })
+}
+
 function walk(ast: SchemaAST.AST): z.ZodTypeAny {
   const cached = walkCache.get(ast)
   if (cached) return cached