Add codex_hook_run analytics event (#17996)

# Why
Add product analytics for hook handler executions so we can understand
which hooks are running, where they came from, and whether they
completed, failed, stopped, or blocked work.

# What
- add the new `codex_hook_run` analytics event and payload plumbing in
`codex-rs/analytics`
- emit hook-run analytics from the shared hook completion path in
`codex-rs/core`
- classify hook source from the loaded hook path as `system`, `user`,
`project`, or `unknown`

```
{
  "event_type": "codex_hook_run",
  "event_params": {
    "thread_id": "string",
    "turn_id": "string",
    "model_slug": "string",
    "hook_name": "string, // any HookEventName
    "hook_source": "system | user | project | unknown",
    "status": "completed | failed | stopped | blocked"
  }
}
```

---------

Co-authored-by: Codex <noreply@openai.com>

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

@@ -106,6 +106,14 @@
         "scope": {
           "$ref": "#/definitions/HookScope"
         },
+        "source": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/HookSource"
+            }
+          ],
+          "default": "unknown"
+        },
         "sourcePath": {
           "$ref": "#/definitions/AbsolutePathBuf"
         },
@@ -143,6 +151,19 @@
         "turn"
       ],
       "type": "string"
+    },
+    "HookSource": {
+      "enum": [
+        "system",
+        "user",
+        "project",
+        "mdm",
+        "sessionFlags",
+        "legacyManagedConfigFile",
+        "legacyManagedConfigMdm",
+        "unknown"
+      ],
+      "type": "string"
     }
   },
   "properties": {