fix(todo-continuation): normalize prompt agent

Todo continuation could reinject with a lowercase built-in config key such as hephaestus when no registered alias was available. OpenCode prompt dispatch expects the prompt-facing agent name, so the continuation failed with an agent-not-found error.

Normalize the dispatch fallback through the existing prompt agent display-name resolver and pin the lowercase Hephaestus regression.

src/hooks/todo-continuation-enforcer/continuation-injection-agent-name.test.ts

@@ -0,0 +1,48 @@
+/// <reference path="../../../bun-test.d.ts" />
+
+import { afterEach, describe, expect, test } from "bun:test"
+
+import { unsafeTestValue } from "../../../test-support/unsafe-test-value"
+
+import { releaseAllPromptAsyncReservationsForTesting } from "../shared/prompt-async-gate"
+import { injectContinuation } from "./continuation-injection"
+
+describe("injectContinuation agent names", () => {
+  afterEach(() => {
+    releaseAllPromptAsyncReservationsForTesting()
+  })
+
+  test("#given resolved agent is a lowercase built-in config key #when continuation is injected #then promptAsync receives the registered display name", async () => {
+    // given
+    let capturedAgent: string | undefined
+    const ctx = unsafeTestValue<Parameters<typeof injectContinuation>[0]["ctx"]>({
+      directory: "/tmp/test",
+      client: {
+        session: {
+          todo: async () => ({ data: [{ id: "1", content: "todo", status: "pending", priority: "high" }] }),
+          promptAsync: async (input: { body: { agent?: string } }) => {
+            capturedAgent = input.body.agent
+            return {}
+          },
+        },
+      },
+    })
+    const sessionStateStore = unsafeTestValue<Parameters<typeof injectContinuation>[0]["sessionStateStore"]>({
+      getExistingState: () => ({ inFlight: false, lastInjectedAt: 0, consecutiveFailures: 0 }),
+    })
+
+    // when
+    await injectContinuation({
+      ctx,
+      sessionID: "ses_lowercase_builtin_agent",
+      resolvedInfo: {
+        agent: "hephaestus",
+        model: { providerID: "openai", modelID: "gpt-5.5" },
+      },
+      sessionStateStore,
+    })
+
+    // then
+    expect(capturedAgent).toBe("Hephaestus - Deep Agent")
+  })
+})