test: close PTY stderr oracle

Require exactly one deterministic reconnect status and reject unrelated ANSI output through the mutation gate.

agent-session-id: ed878dac-3735-4276-b3e0-ea1b1cd65291
agent-tool: Codex CLI
agent-tool-version: 0.145.0
agent-model: unknown
agent-runtime-profile: /nix/store/mnx8agbdq3wiyb6vz63lhgscgazkrn98-coding-agent-runtime-profile/share/coding-agents/profile.json
agent-skills-manifest: /nix/store/5r69m9k2llmri3na81518zx0a7y0d3cn-agent-skills-corpus/share/agent-skills/manifest.json
tooling-profile: dotfiles@0fb7e03

Author: schickling-assistant

cells/pty-attach-machine-stream/fixture/check-stream.mjs

@@ -87,8 +87,9 @@ const validateFinal = (data, expectedGeometries, stdout = Buffer.alloc(0), stder
     throw new Error("unexpected packet type in machine stream")
   }
   if (stdout.length !== 0) throw new Error("machine attach wrote to stdout")
-  for (const marker of ["INITIAL_COLOR_61e8", "AFTER_DROP_61e8", "FINAL_DATA_61e8"]) {
-    if (stderr.includes(Buffer.from(marker))) throw new Error(`terminal marker leaked to stderr: ${marker}`)
+  const reconnectStatus = Buffer.from("\r\n[reconnecting… — Ctrl-\\ or Ctrl-C to stop]\r\n")
+  if (!stderr.equals(reconnectStatus)) {
+    throw new Error("machine attach stderr was not exactly one reconnect status")
   }
 }
 
@@ -102,16 +103,17 @@ const selfTest = () => {
     frame(0, Buffer.from("FINAL_DATA_61e8")), frame(4, Buffer.alloc(0)),
   ]
   const valid = Buffer.concat(packets)
-  validateFinal(valid, expected)
+  const reconnectStatus = Buffer.from("\r\n[reconnecting… — Ctrl-\\ or Ctrl-C to stop]\r\n")
+  validateFinal(valid, expected, Buffer.alloc(0), reconnectStatus)
   const uncolored = Buffer.from("\x1b[HINITIAL_COLOR_61e8\x1b[0m")
   const mutations = [
     () => validateFinal(Buffer.concat([frame(10, geometry(1, 1)), ...packets.slice(1)]), expected),
     () => validateFinal(Buffer.concat([frame(10, geometry(24, 80)), frame(5, uncolored), ...packets.slice(2)]), expected),
     () => validateFinal(Buffer.concat([packets[0], packets[1], packets[2], frame(5, colored), ...packets.slice(4)]), expected),
     () => validateFinal(Buffer.concat([...packets.slice(0, 4), packets[5], packets[4]]), expected),
     () => validateFinal(valid.subarray(0, valid.length - 1), expected),
-    () => validateFinal(valid, expected, Buffer.from("unexpected")),
-    () => validateFinal(valid, expected, Buffer.alloc(0), Buffer.from("FINAL_DATA_61e8")),
+    () => validateFinal(valid, expected, Buffer.from("unexpected"), reconnectStatus),
+    () => validateFinal(valid, expected, Buffer.alloc(0), Buffer.concat([reconnectStatus, Buffer.from("\x1b[32mLEAK")])),
   ]
   for (const mutate of mutations) assert.throws(mutate)
   console.log("ORACLE-MUTATIONS-GREEN-61e8")