fix(test): register session agent in boulder continuation tests for CI isolation

Tests relied on leaked agent registration from other tests when run locally.
In CI, each test batch runs in isolation so the session agent was null,
causing getLastAgentFromSession to return null and the test to incorrectly
pass (return true instead of false).

src/cli/run/completion-continuation.test.ts

@@ -119,6 +119,7 @@ describe("checkCompletionConditions continuation coverage", () => {
 
     const ctx = createMockContext(directory)
     ctx.sessionID = "child-session"
+    setSessionAgent("child-session", "atlas")
     ctx.client.session.get = mock(async ({ path }: { path: { id: string } }) => ({
       data: {
         id: path.id,
@@ -400,6 +401,7 @@ describe("checkCompletionConditions continuation coverage", () => {
 
     const ctx = createMockContext(directory)
     ctx.sessionID = "ses_child_after_compaction"
+    setSessionAgent("ses_child_after_compaction", "atlas")
     ctx.client.session.get = mock(async ({ path }: { path: { id: string } }) => ({
       data: {
         id: path.id,