refactor: switch codex runner from app-server to SDK

Replace raw JSON-RPC app-server protocol with @openai/codex-sdk.
The SDK wraps `codex exec` which ensures complete task execution per
turn, fixing the issue where app-server mode ended turns prematurely
(agent saying "하겠습니다" without doing the work).

Also fix AGENTS.md copy in agent-runner (was copying instructions.md
which Codex CLI doesn't read).

package-lock.json

@@ -1982,6 +1982,7 @@
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       "dev": true,
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=12"
       },
@@ -2548,6 +2549,7 @@
       "integrity": "sha512-5C1sg4USs1lfG0GFb2RLXsdpXqBSEhAaA/0kPL01wxzpMqLILNxIxIOKiILz+cdg/pLnOUxFYOR5yhHU666wbw==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "esbuild": "~0.27.0",
         "get-tsconfig": "^4.7.5"
@@ -2615,6 +2617,7 @@
       "integrity": "sha512-w+N7Hifpc3gRjZ63vYBXA56dvvRlNWRczTdmCBBa+CotUzAPf5b7YMdMR/8CQoeYE5LX3W4wj6RYTgonm1b9DA==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "esbuild": "^0.27.0",
         "fdir": "^6.5.0",
@@ -2690,6 +2693,7 @@
       "integrity": "sha512-hOQuK7h0FGKgBAas7v0mSAsnvrIgAvWmRFjmzpJ7SwFHH3g1k2u37JtYwOwmEKhK6ZO3v9ggDBBm0La1LCK4uQ==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@vitest/expect": "4.0.18",
         "@vitest/mocker": "4.0.18",
@@ -2811,6 +2815,7 @@
       "resolved": "https://registry.npmjs.org/yaml/-/yaml-2.8.2.tgz",
       "integrity": "sha512-mplynKqc1C2hTVYxd0PU2xQAc22TI1vShAYGksCCfxbn/dFwnHTNi1bvYsBTkhdUNtGIf5xNOg938rrSSYvS9A==",
       "license": "ISC",
+      "peer": true,
       "bin": {
         "yaml": "bin.mjs"
       },