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`







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[//]: # (BEGIN SAPLING FOOTER)
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with [ReviewStack](https://reviewstack.dev/openai/codex/pull/18279).
* #18288
* #18287
* #18286
* #18285
* #18284
* #18283
* #18282
* #18281
* #18280
* __->__ #18279

codex-rs/core/tests/suite/prompt_caching.rs

@@ -444,6 +444,7 @@ async fn overrides_turn_context_but_keeps_cached_prefix_and_key_constant() -> an
             approval_policy: Some(AskForApproval::Never),
             approvals_reviewer: None,
             sandbox_policy: Some(new_policy.clone()),
+            permission_profile: None,
             windows_sandbox_level: None,
             model: None,
             effort: Some(Some(ReasoningEffort::High)),
@@ -529,6 +530,7 @@ async fn override_before_first_turn_emits_environment_context() -> anyhow::Resul
             approval_policy: Some(AskForApproval::Never),
             approvals_reviewer: None,
             sandbox_policy: None,
+            permission_profile: None,
             windows_sandbox_level: None,
             model: Some("gpt-5.4".to_string()),
             effort: Some(Some(ReasoningEffort::Low)),