fix(team-mailbox): dedupe pendingInjectedMessageIds across turns

Without ack between turns the same unread messageIds would re-enter
pendingInjectedMessageIds on every poll, unboundedly growing the list
(state.json observed 8-12 copies of the same id under runtime pressure).

Wrap the append with a Set so pending state stays idempotent regardless
of how many times the transform hook polls before ack lands.

src/features/team-mode/team-mailbox/poll.test.ts

@@ -7,7 +7,7 @@ import { tmpdir } from "node:os"
 import path from "node:path"
 
 import { TeamModeConfigSchema } from "../../../config/schema/team-mode"
-import { createRuntimeState } from "../team-state-store/store"
+import { createRuntimeState, loadRuntimeState } from "../team-state-store/store"
 import type { TeamSpec } from "../types"
 import { sendMessage } from "./send"
 
@@ -144,4 +144,28 @@ describe("pollAndBuildInjection", () => {
     expect(inboxEntries).toContain(`${secondMessageId}.json`)
     expect(inboxEntries).not.toContain("processed")
   })
+
+  test("deduplicates pendingInjectedMessageIds when the same unread message surfaces across turns", async () => {
+    // given
+    const { teamRunId, config } = await setupRuntime(["m1"])
+    const messageId = randomUUID()
+    await sendMessage({
+      version: 1,
+      messageId,
+      from: "lead",
+      to: "m1",
+      kind: "message",
+      body: "persistent",
+      timestamp: 100,
+    }, teamRunId, config, { isLead: true, activeMembers: ["m1"] })
+
+    // when
+    await pollAndBuildInjection("session-1", "m1", teamRunId, config, "turn-A")
+    await pollAndBuildInjection("session-1", "m1", teamRunId, config, "turn-B")
+    const runtimeState = await loadRuntimeState(teamRunId, config)
+    const member = runtimeState.members.find((entry) => entry.name === "m1")
+
+    // then
+    expect(member?.pendingInjectedMessageIds).toEqual([messageId])
+  })
 })

src/features/team-mode/team-mailbox/poll.ts

@@ -78,7 +78,7 @@ export async function pollAndBuildInjection(
         ? {
           ...member,
           lastInjectedTurnMarker: turnMarker,
-          pendingInjectedMessageIds: [...member.pendingInjectedMessageIds, ...messageIds],
+          pendingInjectedMessageIds: Array.from(new Set([...member.pendingInjectedMessageIds, ...messageIds])),
         }
         : member
     )),