codex: support hooks in config.toml and requirements.toml (#18893)

## Summary

Support the existing hooks schema in inline TOML so hooks can be
configured from both `config.toml` and enterprise-managed
`requirements.toml` without requiring a separate `hooks.json` payload.

This gives enterprise admins a way to ship managed hook policy through
the existing requirements channel while still leaving script delivery to
MDM or other device-management tooling, and it keeps `hooks.json`
working unchanged for existing users.

This also lays the groundwork for follow-on managed filtering work such
as #15937, while continuing to respect project trust gating from #14718.
It does **not** implement `allow_managed_hooks_only` itself.

NOTE: yes, it's a bit unfortunate that the toml isn't formatted as
closely as normal to our default styling. This is because we're trying
to stay compatible with the spec for plugins/hooks that we'll need to
support & the main usecase here is embedding into requirements.toml

## What changed

- moved the shared hook serde model out of `codex-rs/hooks` into
`codex-rs/config` so the same schema can power `hooks.json`, inline
`config.toml` hooks, and managed `requirements.toml` hooks
- added `hooks` support to both `ConfigToml` and
`ConfigRequirementsToml`, including requirements-side `managed_dir` /
`windows_managed_dir`
- treated requirements-managed hooks as one constrained value via
`Constrained`, so managed hook policy is merged atomically and cannot
drift across requirement sources
- updated hook discovery to load requirements-managed hooks first, then
per-layer `hooks.json`, then per-layer inline TOML hooks, with a warning
when a single layer defines both representations
- threaded managed hook metadata through discovered handlers and exposed
requirements hooks in app-server responses, generated schemas, and
`/debug-config`
- added hook/config coverage in `codex-rs/config`, `codex-rs/hooks`,
`codex-rs/core/src/config_loader/tests.rs`, and
`codex-rs/core/tests/suite/hooks.rs`

## Testing

- `cargo test -p codex-config`
- `cargo test -p codex-hooks`
- `cargo test -p codex-app-server config_api`

## Documentation

Companion updates are needed in the developers website repo for:

- the hooks guide
- the config reference, sample, basic, and advanced pages
- the enterprise managed configuration guide

---------

Co-authored-by: Michael Bolin <mbolin@openai.com>

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

@@ -111,6 +111,161 @@
       },
       "type": "object"
     },
+    "ConfiguredHookHandler": {
+      "oneOf": [
+        {
+          "properties": {
+            "async": {
+              "type": "boolean"
+            },
+            "command": {
+              "type": "string"
+            },
+            "statusMessage": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "timeoutSec": {
+              "format": "uint64",
+              "minimum": 0.0,
+              "type": [
+                "integer",
+                "null"
+              ]
+            },
+            "type": {
+              "enum": [
+                "command"
+              ],
+              "title": "CommandConfiguredHookHandlerType",
+              "type": "string"
+            }
+          },
+          "required": [
+            "async",
+            "command",
+            "type"
+          ],
+          "title": "CommandConfiguredHookHandler",
+          "type": "object"
+        },
+        {
+          "properties": {
+            "type": {
+              "enum": [
+                "prompt"
+              ],
+              "title": "PromptConfiguredHookHandlerType",
+              "type": "string"
+            }
+          },
+          "required": [
+            "type"
+          ],
+          "title": "PromptConfiguredHookHandler",
+          "type": "object"
+        },
+        {
+          "properties": {
+            "type": {
+              "enum": [
+                "agent"
+              ],
+              "title": "AgentConfiguredHookHandlerType",
+              "type": "string"
+            }
+          },
+          "required": [
+            "type"
+          ],
+          "title": "AgentConfiguredHookHandler",
+          "type": "object"
+        }
+      ]
+    },
+    "ConfiguredHookMatcherGroup": {
+      "properties": {
+        "hooks": {
+          "items": {
+            "$ref": "#/definitions/ConfiguredHookHandler"
+          },
+          "type": "array"
+        },
+        "matcher": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      },
+      "required": [
+        "hooks"
+      ],
+      "type": "object"
+    },
+    "ManagedHooksRequirements": {
+      "properties": {
+        "PermissionRequest": {
+          "items": {
+            "$ref": "#/definitions/ConfiguredHookMatcherGroup"
+          },
+          "type": "array"
+        },
+        "PostToolUse": {
+          "items": {
+            "$ref": "#/definitions/ConfiguredHookMatcherGroup"
+          },
+          "type": "array"
+        },
+        "PreToolUse": {
+          "items": {
+            "$ref": "#/definitions/ConfiguredHookMatcherGroup"
+          },
+          "type": "array"
+        },
+        "SessionStart": {
+          "items": {
+            "$ref": "#/definitions/ConfiguredHookMatcherGroup"
+          },
+          "type": "array"
+        },
+        "Stop": {
+          "items": {
+            "$ref": "#/definitions/ConfiguredHookMatcherGroup"
+          },
+          "type": "array"
+        },
+        "UserPromptSubmit": {
+          "items": {
+            "$ref": "#/definitions/ConfiguredHookMatcherGroup"
+          },
+          "type": "array"
+        },
+        "managedDir": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "windowsManagedDir": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      },
+      "required": [
+        "PermissionRequest",
+        "PostToolUse",
+        "PreToolUse",
+        "SessionStart",
+        "Stop",
+        "UserPromptSubmit"
+      ],
+      "type": "object"
+    },
     "NetworkDomainPermission": {
       "enum": [
         "allow",