Use PathUri in filesystem permission paths for exec-server (#28165)

## Why

Progress towards letting app-server and exec-server run on different
platforms, specifically for sandbox configuration.

## What

- Make the filesystem path containment hierarchy generic, defaulting to
`AbsolutePathBuf` for now.
- Have clients specify `AbsolutePathBuf` or `PathUri` directly where
needed.
- Use `PathUri` throughout exec-server filesystem protocol and trait
boundaries.
- Implement `From` for conversion to path URIs and `TryFrom` for
fallible conversion to absolute paths through the generic type
hierarchy.

codex-rs/protocol/src/permissions.rs

@@ -6,6 +6,7 @@ use std::path::PathBuf;
 
 use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_absolute_path::canonicalize_preserving_symlinks;
+use codex_utils_path_uri::PathUri;
 use globset::GlobBuilder;
 use globset::GlobMatcher;
 use schemars::JsonSchema;
@@ -176,11 +177,31 @@ impl FileSystemSpecialPath {
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize, JsonSchema, TS)]
-pub struct FileSystemSandboxEntry {
-    pub path: FileSystemPath,
+pub struct FileSystemSandboxEntry<PathType = AbsolutePathBuf> {
+    pub path: FileSystemPath<PathType>,
     pub access: FileSystemAccessMode,
 }
 
+impl From<FileSystemSandboxEntry<AbsolutePathBuf>> for FileSystemSandboxEntry<PathUri> {
+    fn from(value: FileSystemSandboxEntry<AbsolutePathBuf>) -> Self {
+        FileSystemSandboxEntry {
+            path: value.path.into(),
+            access: value.access,
+        }
+    }
+}
+
+impl TryFrom<FileSystemSandboxEntry<PathUri>> for FileSystemSandboxEntry<AbsolutePathBuf> {
+    type Error = io::Error;
+
+    fn try_from(value: FileSystemSandboxEntry<PathUri>) -> Result<Self, Self::Error> {
+        Ok(FileSystemSandboxEntry {
+            path: value.path.try_into()?,
+            access: value.access,
+        })
+    }
+}
+
 #[derive(
     Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Display, Default, JsonSchema, TS,
 )]
@@ -338,9 +359,9 @@ enum InvalidDenyReadGlobBehavior {
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize, JsonSchema, TS)]
 #[serde(tag = "type", rename_all = "snake_case")]
 #[ts(tag = "type")]
-pub enum FileSystemPath {
+pub enum FileSystemPath<PathType = AbsolutePathBuf> {
     Path {
-        path: AbsolutePathBuf,
+        path: PathType,
     },
     /// A git-style glob pattern. Pattern entries currently support
     /// FileSystemAccessMode::Deny only.
@@ -352,6 +373,32 @@ pub enum FileSystemPath {
     },
 }
 
+impl From<FileSystemPath<AbsolutePathBuf>> for FileSystemPath<PathUri> {
+    fn from(value: FileSystemPath<AbsolutePathBuf>) -> Self {
+        match value {
+            FileSystemPath::Path { path } => FileSystemPath::Path {
+                path: PathUri::from_abs_path(&path),
+            },
+            FileSystemPath::GlobPattern { pattern } => FileSystemPath::GlobPattern { pattern },
+            FileSystemPath::Special { value } => FileSystemPath::Special { value },
+        }
+    }
+}
+
+impl TryFrom<FileSystemPath<PathUri>> for FileSystemPath<AbsolutePathBuf> {
+    type Error = io::Error;
+
+    fn try_from(value: FileSystemPath<PathUri>) -> Result<Self, Self::Error> {
+        Ok(match value {
+            FileSystemPath::Path { path } => FileSystemPath::Path {
+                path: path.to_abs_path()?,
+            },
+            FileSystemPath::GlobPattern { pattern } => FileSystemPath::GlobPattern { pattern },
+            FileSystemPath::Special { value } => FileSystemPath::Special { value },
+        })
+    }
+}
+
 const PROJECT_ROOTS_GLOB_PATTERN_PREFIX: &str = "codex-project-roots://";
 
 pub fn project_roots_glob_pattern(subpath: &Path) -> String {