Skip missing paths in filesystem sandbox entries (#34598)

## Why

Default read-only protections for project metadata should apply when paths such
as `.git`, `.agents`, and `.codex` exist, without causing sandbox setup to
materialize missing paths as ACL targets.

## What changed

- Add an optional `missing_path_behavior` to filesystem sandbox entries and
  mark default project-metadata protections with `skip`.
- Preserve the behavior through permission transforms and exec/MCP protocol
  serialization while keeping existing path wire variants stable.
- Ignore skip-missing entries when projecting configuration or Windows sandbox
  overrides, while retaining explicit metadata carveouts.

## Testing

- Cover protocol round trips for path and special-path entries.
- Verify default metadata protections and Windows explicit carveout handling.

GitOrigin-RevId: 6df13dadacdd131c44aab9f15a967c81051355c1

codex-rs/windows-sandbox-rs/src/deny_read_resolver.rs

@@ -44,6 +44,7 @@ pub fn resolve_windows_deny_read_paths(
                     pattern: pattern.clone(),
                 },
                 access: FileSystemAccessMode::Deny,
+                missing_path_behavior: None,
             })
             .collect(),
     );
@@ -206,6 +207,7 @@ mod tests {
         FileSystemSandboxEntry {
             path: FileSystemPath::GlobPattern { pattern },
             access: FileSystemAccessMode::Deny,
+            missing_path_behavior: None,
         }
     }
 
@@ -215,6 +217,7 @@ mod tests {
                 path: AbsolutePathBuf::from_absolute_path(path).expect("absolute path"),
             },
             access: FileSystemAccessMode::Deny,
+            missing_path_behavior: None,
         }
     }
 

codex-rs/windows-sandbox-rs/src/resolved_permissions.rs

@@ -173,7 +173,7 @@ impl ResolvedWindowsSandboxPermissions {
         self.file_system
             .entries
             .iter()
-            .any(|FileSystemSandboxEntry { path, access }| {
+            .any(|FileSystemSandboxEntry { path, access, .. }| {
                 matches!(
                     path,
                     FileSystemPath::Special {
@@ -258,6 +258,7 @@ mod tests {
                         value: FileSystemSpecialPath::project_roots(/*subpath*/ None),
                     },
                     access: FileSystemAccessMode::Write,
+                    missing_path_behavior: None,
                 }],
                 glob_scan_max_depth: None,
             },
@@ -298,18 +299,21 @@ mod tests {
                             value: FileSystemSpecialPath::project_roots(/*subpath*/ None),
                         },
                         access: FileSystemAccessMode::Write,
+                        missing_path_behavior: None,
                     },
                     FileSystemSandboxEntry {
                         path: FileSystemPath::Special {
                             value: FileSystemSpecialPath::project_roots(Some(".git".into())),
                         },
                         access: FileSystemAccessMode::Deny,
+                        missing_path_behavior: None,
                     },
                     FileSystemSandboxEntry {
                         path: FileSystemPath::GlobPattern {
                             pattern: project_roots_glob_pattern(Path::new("**/*.env")),
                         },
                         access: FileSystemAccessMode::Deny,
+                        missing_path_behavior: None,
                     },
                 ],
                 glob_scan_max_depth: None,
@@ -332,24 +336,28 @@ mod tests {
                         path: first.clone(),
                     },
                     access: FileSystemAccessMode::Write,
+                    missing_path_behavior: None,
                 },
                 FileSystemSandboxEntry {
                     path: FileSystemPath::Path {
                         path: second.clone(),
                     },
                     access: FileSystemAccessMode::Write,
+                    missing_path_behavior: None,
                 },
                 FileSystemSandboxEntry {
                     path: FileSystemPath::Path {
                         path: first.join(".git"),
                     },
                     access: FileSystemAccessMode::Deny,
+                    missing_path_behavior: None,
                 },
                 FileSystemSandboxEntry {
                     path: FileSystemPath::Path {
                         path: second.join(".git"),
                     },
                     access: FileSystemAccessMode::Deny,
+                    missing_path_behavior: None,
                 },
                 FileSystemSandboxEntry {
                     path: FileSystemPath::GlobPattern {
@@ -361,6 +369,7 @@ mod tests {
                         .into_owned(),
                     },
                     access: FileSystemAccessMode::Deny,
+                    missing_path_behavior: None,
                 },
                 FileSystemSandboxEntry {
                     path: FileSystemPath::GlobPattern {
@@ -372,6 +381,7 @@ mod tests {
                         .into_owned(),
                     },
                     access: FileSystemAccessMode::Deny,
+                    missing_path_behavior: None,
                 },
             ])
         );
@@ -455,6 +465,7 @@ mod tests {
                         value: FileSystemSpecialPath::Root,
                     },
                     access: FileSystemAccessMode::Write,
+                    missing_path_behavior: None,
                 }],
                 glob_scan_max_depth: None,
             },