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/tools/call-omo-agent/session-creator.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, test } from "bun:test"
 
 import { createOrGetSession } from "./session-creator"
 import { _resetForTesting, subagentSessions } from "../../features/claude-code-session-state"
+import { unsafeTestValue } from "../../../test-support/unsafe-test-value"
 
 describe("call-omo-agent createOrGetSession", () => {
   test("creates child session without overriding permission and tracks it as subagent session", async () => {
@@ -37,12 +38,12 @@ describe("call-omo-agent createOrGetSession", () => {
     }
 
     // when
-    const result = await createOrGetSession(testCoerce(args), testCoerce(toolContext), testCoerce(ctx))
+    const result = await createOrGetSession(unsafeTestValue(args), unsafeTestValue(toolContext), unsafeTestValue(ctx))
 
     // then
     expect(result).toEqual({ sessionID: "ses_child", isNew: true })
     expect(createCalls).toHaveLength(1)
-    const createBody = (testCoerce(createCalls[0]))?.body
+    const createBody = (unsafeTestValue(createCalls[0]))?.body
     expect(createBody?.parentID).toBe("ses_parent")
     expect(createBody?.permission).toBeUndefined()
     expect(subagentSessions.has("ses_child")).toBe(true)