Take the audit log and file checksums out of the chat surface

The thread panel rendered an "Audit" feed — "Chat message sent", "Task
run completed", "Approval requested" rows with monospace timestamps —
a server log sitting inside a conversation. Attachments showed an eight-
character SHA-256 fragment next to the file type. Neither belongs in a
surface a non-technical operator reads as people talking.

Remove the audit replay from the chat thread (and its now-dead
replayEventsForThread/auditPayload plumbing) and drop the checksum from
the attachment card. The audit trail itself is unchanged — it is still
recorded and still shown on the task activity tab. The e2e thread check
now asserts the reply box, not the log.

AgentCompany-New/tests/e2e/desktop.spec.ts

@@ -102,9 +102,7 @@ test("onboards, hires, and creates work in the Electron shell", async () => {
     await expect(page.getByText("@Board").first()).toBeVisible();
     await expect(page.getByText("/escalate").first()).toBeVisible();
     await page.getByRole("button", { name: "Open thread" }).first().click();
-    await expect(page.getByText("Audit")).toBeVisible();
-    await expect(page.getByText("Chat message sent").first()).toBeVisible();
-    await expect(page.getByText("Approval requested").first()).toBeVisible();
+    await expect(page.getByRole("textbox", { name: "Thread reply" })).toBeVisible();
     await page.getByRole("button", { name: "Approvals" }).click();
     await expect(page.getByText("Escalate release").first()).toBeVisible();