feat(core): add session metadata support (#23068)

Co-authored-by: Aiden Cline <aidenpcline@gmail.com>

packages/opencode/test/session/session.test.ts

@@ -184,4 +184,35 @@ describe("Session", () => {
       expect(Exit.isFailure(getExit)).toBe(true)
     }),
   )
+
+  it.instance("persists metadata and copies it on fork by default", () =>
+    Effect.gen(function* () {
+      const session = yield* SessionNs.Service
+      const meta = { source: "sdk", trace: { id: "abc" } }
+      const created = yield* Effect.acquireRelease(session.create({ title: "with-meta", metadata: meta }), (info) =>
+        session.remove(info.id).pipe(Effect.ignore),
+      )
+      const saved = yield* session.get(created.id)
+      const fork = yield* Effect.acquireRelease(session.fork({ sessionID: created.id }), (info) =>
+        session.remove(info.id).pipe(Effect.ignore),
+      )
+
+      expect(saved.metadata).toEqual(meta)
+      expect(fork.metadata).toEqual(meta)
+      expect(fork.metadata).not.toBe(meta)
+    }),
+  )
+
+  it.instance("omits metadata when not provided", () =>
+    Effect.gen(function* () {
+      const session = yield* SessionNs.Service
+      const created = yield* Effect.acquireRelease(session.create({ title: "empty-meta" }), (info) =>
+        session.remove(info.id).pipe(Effect.ignore),
+      )
+      const saved = yield* session.get(created.id)
+
+      expect(created.metadata).toBeUndefined()
+      expect(saved.metadata).toBeUndefined()
+    }),
+  )
 })