feat(core): port v2 runtime fixes onto dev

Cherry-picks the packages/core changes from the v2 branch onto dev:
- combined ordered stdout/stderr in AppProcess + bash structured output
- edit/apply-patch return FileDiff info with status and line stats
- ignore no-op model switches; record reasoning timestamps
- return unexpected local tool defects to the model and continue
- keep OAuth account metadata out of request bodies
- nest OpenAI reasoning effort/summary options
- load OpenCode provider config asynchronously; batch plugin boot
- export latest public event manifest

Includes the supporting schema reasoning time field and regenerated
client/SDK types.

packages/core/test/session-create.test.ts

@@ -377,7 +377,7 @@ describe("SessionV2.create", () => {
     }),
   )
 
-  it.effect("persists repeated switches as distinct durable Session events", () =>
+  it.effect("ignores a model switch when the selected model is unchanged", () =>
     Effect.gen(function* () {
       const session = yield* SessionV2.Service
       const created = yield* session.create({ location })
@@ -389,11 +389,29 @@ describe("SessionV2.create", () => {
       const { db } = yield* Database.Service
       expect(
         yield* db.select().from(EventTable).where(eq(EventTable.aggregate_id, created.id)).all().pipe(Effect.orDie),
-      ).toHaveLength(3)
+      ).toHaveLength(2)
       expect(yield* session.get(created.id)).toMatchObject({ model })
     }),
   )
 
+  it.effect("treats an omitted variant as the default variant", () =>
+    Effect.gen(function* () {
+      const session = yield* SessionV2.Service
+      const model = ModelV2.Ref.make({ id: ModelV2.ID.make("sonnet"), providerID: ProviderV2.ID.anthropic })
+      const created = yield* session.create({ location, model })
+
+      yield* session.switchModel({
+        sessionID: created.id,
+        model: ModelV2.Ref.make({ ...model, variant: ModelV2.VariantID.make("default") }),
+      })
+
+      const { db } = yield* Database.Service
+      expect(
+        yield* db.select().from(EventTable).where(eq(EventTable.aggregate_id, created.id)).all().pipe(Effect.orDie),
+      ).toHaveLength(1)
+    }),
+  )
+
   it.effect("rejects a model switch for a missing Session", () =>
     Effect.gen(function* () {
       const session = yield* SessionV2.Service