fix(coding-agent): kernel test fixtures speak protocol 3

The fake-runtime fixtures in the REPL corruption and provisioner suites
still announced protocol 2 after the runtime moved to
REPL_PROTOCOL_VERSION = 3, so 23 tests failed deterministically on a
clean checkout with the protocol-mismatch error instead of exercising
their scenarios. The constant is module-private in repl-manager.ts, so
the fixtures use the literal 3.

Author: snimu

packages/coding-agent/test/ipython-provisioner.test.ts

@@ -73,7 +73,7 @@ function writeFakeReplRuntime(markerPath: string): string {
 const fs = require("node:fs");
 const readline = require("node:readline");
 const emit = (event) => process.stdout.write(JSON.stringify(event) + "\\n");
-emit({ event: "ready", protocol: 2, python: process.version });
+emit({ event: "ready", protocol: 3, python: process.version });
 const input = readline.createInterface({ input: process.stdin });
 input.on("line", (line) => {
 	const request = JSON.parse(line);

packages/coding-agent/test/repl-kernel-protocol-corruption.test.ts

@@ -32,10 +32,10 @@ if (fs.existsSync(process.env.FAKE_REPL_CORRUPT_BOOT)) {
   process.stdout.write("BROKEN-BOOT\\n");
 } else if (fs.existsSync(process.env.FAKE_REPL_READY_WITH_GARBAGE)) {
   process.stdout.write(
-    JSON.stringify({ event: "ready", protocol: 2, python: process.version }) + "\\nBROKEN-WITH-READY\\n",
+    JSON.stringify({ event: "ready", protocol: 3, python: process.version }) + "\\nBROKEN-WITH-READY\\n",
   );
 } else if (!(count > 1 && fs.existsSync(process.env.FAKE_REPL_DELAY_READY))) {
-  emit({ event: "ready", protocol: 2, python: process.version });
+  emit({ event: "ready", protocol: 3, python: process.version });
 }
 const input = readline.createInterface({ input: process.stdin });
 input.on("line", (line) => {