Remove generated-default filesystem path variants (#33632)

## What changed

- Represent built-in filesystem policy entries with the same `Path` and
  `Special` variants used by other entries.
- Remove generated-default filtering from Windows sandbox policy resolution and
  simplify elevated deny-write handling to rely on direct-runtime enforcement
  and the legacy policy projection.
- Update protocol conversions, policy transforms, and profile expectations for
  the reduced filesystem path model.

GitOrigin-RevId: a65793e6855a03d52a575e82cb3d4b9b2e32db5c

codex-rs/app-server-protocol/src/protocol/v2/permissions.rs

@@ -312,13 +312,11 @@ pub enum FileSystemPath {
 impl From<CoreFileSystemPath> for FileSystemPath {
     fn from(value: CoreFileSystemPath) -> Self {
         match value {
-            CoreFileSystemPath::Path { path }
-            | CoreFileSystemPath::GeneratedDefaultPath { path } => Self::Path {
+            CoreFileSystemPath::Path { path } => Self::Path {
                 path: LegacyAppPathString::from_abs_path(&path),
             },
             CoreFileSystemPath::GlobPattern { pattern } => Self::GlobPattern { pattern },
-            CoreFileSystemPath::Special { value }
-            | CoreFileSystemPath::GeneratedDefaultSpecial { value } => Self::Special {
+            CoreFileSystemPath::Special { value } => Self::Special {
                 value: value.into(),
             },
         }