app-server: accept permission profile overrides (#18279)

## Why

`PermissionProfile` is becoming the canonical permissions shape shared
by core and app-server. After app-server responses expose the active
profile, clients need to be able to send that same shape back when
starting, resuming, forking, or overriding a turn instead of translating
through the legacy `sandbox`/`sandboxPolicy` shorthands.

This still needs to preserve the existing requirements/platform
enforcement model. A profile-shaped request can be downgraded or
rejected by constraints, but the server should keep the user's
elevated-access intent for project trust decisions. Turn-level profile
overrides also need to retain existing read protections, including
deny-read entries and bounded glob-scan metadata, so a permission
override cannot accidentally drop configured protections such as
`**/*.env = deny`.

## What changed

- Adds optional `permissionProfile` request fields to `thread/start`,
`thread/resume`, `thread/fork`, and `turn/start`.
- Rejects ambiguous requests that specify both `permissionProfile` and
the legacy `sandbox`/`sandboxPolicy` fields, including running-thread
resume requests.
- Converts profile-shaped overrides into core runtime filesystem/network
permissions while continuing to derive the constrained legacy sandbox
projection used by existing execution paths.
- Preserves project-trust intent for profile overrides that are
equivalent to workspace-write or full-access sandbox requests.
- Preserves existing deny-read entries and `globScanMaxDepth` when
applying turn-level `permissionProfile` overrides.
- Updates app-server docs plus generated JSON/TypeScript schema fixtures
and regression coverage.

## Verification

- `cargo test -p codex-app-server-protocol schema_fixtures`
- `cargo test -p codex-core
session_configuration_apply_permission_profile_preserves_existing_deny_read_entries`







---
[//]: # (BEGIN SAPLING FOOTER)
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with [ReviewStack](https://reviewstack.dev/openai/codex/pull/18279).
* #18288
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* #18286
* #18285
* #18284
* #18283
* #18282
* #18281
* #18280
* __->__ #18279

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -14142,6 +14142,17 @@
               "null"
             ]
           },
+          "permissionProfile": {
+            "anyOf": [
+              {
+                "$ref": "#/definitions/v2/PermissionProfile"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Full permissions override for the forked thread. Cannot be combined with `sandbox`."
+          },
           "sandbox": {
             "anyOf": [
               {
@@ -15560,6 +15571,17 @@
               "null"
             ]
           },
+          "permissionProfile": {
+            "anyOf": [
+              {
+                "$ref": "#/definitions/v2/PermissionProfile"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Full permissions override for the resumed thread. Cannot be combined with `sandbox`."
+          },
           "personality": {
             "anyOf": [
               {
@@ -15866,6 +15888,17 @@
               "null"
             ]
           },
+          "permissionProfile": {
+            "anyOf": [
+              {
+                "$ref": "#/definitions/v2/PermissionProfile"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Full permissions override for this thread. Cannot be combined with `sandbox`."
+          },
           "personality": {
             "anyOf": [
               {
@@ -16671,6 +16704,17 @@
           "outputSchema": {
             "description": "Optional JSON Schema used to constrain the final assistant message for this turn."
           },
+          "permissionProfile": {
+            "anyOf": [
+              {
+                "$ref": "#/definitions/v2/PermissionProfile"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Override the full permissions profile for this turn and subsequent turns. Cannot be combined with `sandboxPolicy`."
+          },
           "personality": {
             "anyOf": [
               {