test: make unsafe test coercion explicit

Move test coercion out of a hidden global and require each test to import the helper so review tools and runtime scripts can see the unsafe boundary.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/runtime-fallback/fallback-models.test.ts

@@ -2,6 +2,7 @@ import { afterEach, describe, expect, test } from "bun:test"
 
 import { getFallbackModelsForSession } from "./fallback-models"
 import { SessionCategoryRegistry } from "../../shared/session-category-registry"
+import { unsafeTestValue } from "../../../test-support/unsafe-test-value"
 
 describe("runtime-fallback fallback-models", () => {
   afterEach(() => {
@@ -12,7 +13,7 @@ describe("runtime-fallback fallback-models", () => {
     //#given
     const sessionID = "ses_runtime_fallback_category"
     SessionCategoryRegistry.register(sessionID, "quick")
-    const pluginConfig = testCoerce({
+    const pluginConfig = unsafeTestValue({
       categories: {
         quick: {
           fallback_models: ["openai/gpt-5.2", "anthropic/claude-opus-4-7"],
@@ -29,7 +30,7 @@ describe("runtime-fallback fallback-models", () => {
 
   test("uses agent-specific fallback_models when agent is resolved", () => {
     //#given
-    const pluginConfig = testCoerce({
+    const pluginConfig = unsafeTestValue({
       agents: {
         oracle: {
           fallback_models: ["openai/gpt-5.2", "anthropic/claude-opus-4-7"],
@@ -46,7 +47,7 @@ describe("runtime-fallback fallback-models", () => {
 
   test("does not fall back to another agent chain when agent cannot be resolved", () => {
     //#given
-    const pluginConfig = testCoerce({
+    const pluginConfig = unsafeTestValue({
       agents: {
         sisyphus: {
           fallback_models: ["quotio/gpt-5.2", "quotio/glm-5", "quotio/kimi-k2.5"],

src/hooks/runtime-fallback/index.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, test, beforeEach, afterEach, mock } from "bun:test"
 import type { RuntimeFallbackConfig, OhMyOpenCodeConfig } from "../../config"
 import * as loggerModule from "../../shared/logger"
 import { SessionCategoryRegistry } from "../../shared/session-category-registry"
+import { unsafeTestValue } from "../../../test-support/unsafe-test-value"
 
 type RuntimeFallbackModule = typeof import("./hook")
 
@@ -41,7 +42,7 @@ describe("runtime-fallback", () => {
       abort?: (args: unknown) => Promise<unknown>
     }
   }) {
-    return testCoerce({
+    return unsafeTestValue({
       client: {
         tui: {
           showToast: async (opts: { body: { title: string; message: string; variant: string; duration: number } }) => {