feat: vendor app-server protocol schema fixtures (#10371)

Similar to what @sayan-oai did in openai/codex#8956 for
`config.schema.json`, this PR updates the repo so that it includes the
output of `codex app-server generate-json-schema` and `codex app-server
generate-ts` and adds a test to verify it is in sync with the current
code.

Motivation:
- This makes any schema changes introduced by a PR transparent during
code review.
- In particular, this should help us catch PRs that would introduce a
non-backwards-compatible change to the app schema (eventually, this
should also be enforced by tooling).
- Once https://github.com/openai/codex/pull/10231 is in to formalize the
notion of "experimental" fields, we can work on ensuring the
non-experimental bits are backwards-compatible.

`codex-rs/app-server-protocol/tests/schema_fixtures.rs` was added as the
test and `just write-app-server-schema` can be use to generate the
vendored schema files.

Incidentally, when I run:

```
rg _ codex-rs/app-server-protocol/schema/typescript/v2
```

I see a number of `snake_case` names that should be `camelCase`.

codex-rs/app-server-protocol/schema/json/v2/ConfigWarningNotification.json

@@ -0,0 +1,77 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "TextPosition": {
+      "properties": {
+        "column": {
+          "description": "1-based column number (in Unicode scalar values).",
+          "format": "uint",
+          "minimum": 0.0,
+          "type": "integer"
+        },
+        "line": {
+          "description": "1-based line number.",
+          "format": "uint",
+          "minimum": 0.0,
+          "type": "integer"
+        }
+      },
+      "required": [
+        "column",
+        "line"
+      ],
+      "type": "object"
+    },
+    "TextRange": {
+      "properties": {
+        "end": {
+          "$ref": "#/definitions/TextPosition"
+        },
+        "start": {
+          "$ref": "#/definitions/TextPosition"
+        }
+      },
+      "required": [
+        "end",
+        "start"
+      ],
+      "type": "object"
+    }
+  },
+  "properties": {
+    "details": {
+      "description": "Optional extra guidance or error details.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "path": {
+      "description": "Optional path to the config file that triggered the warning.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "range": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/TextRange"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "description": "Optional range for the error location inside the config file."
+    },
+    "summary": {
+      "description": "Concise summary of the warning.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "summary"
+  ],
+  "title": "ConfigWarningNotification",
+  "type": "object"
+}