path-uri: clarify host-native path conversion (#29501)

## Why

Downstream refactors are producing confusing code with this
functionality having a very generic name. Encoding the specific
conversion approach in the method name makes it clearer.

## What

Rename `PathUri::from_path` to `PathUri::from_host_native_path` and
update its Rust call sites.

codex-rs/exec-server/src/server/file_system_handler.rs

@@ -274,7 +274,7 @@ mod tests {
         )
         .expect("runtime paths");
         let handler = FileSystemHandler::new(runtime_paths);
-        let sandbox_cwd = PathUri::from_path(temp_dir.path()).expect("tempdir URI");
+        let sandbox_cwd = PathUri::from_host_native_path(temp_dir.path()).expect("tempdir URI");
         let sandbox_context = |sandbox_policy| {
             FileSystemSandboxContext::from_legacy_sandbox_policy(
                 sandbox_policy,
@@ -292,7 +292,8 @@ mod tests {
                 },
             ),
         ] {
-            let path = PathUri::from_path(temp_dir.path().join(file_name)).expect("path URI");
+            let path =
+                PathUri::from_host_native_path(temp_dir.path().join(file_name)).expect("path URI");
 
             handler
                 .write_file(FsWriteFileParams {
@@ -312,7 +313,7 @@ mod tests {
                 .expect("canonicalize file");
             assert_eq!(
                 canonicalized.path,
-                PathUri::from_path(
+                PathUri::from_host_native_path(
                     std::fs::canonicalize(temp_dir.path().join(file_name)).expect("canonical path"),
                 )
                 .expect("canonical path URI"),

codex-rs/exec-server/src/server/handler/tests.rs

@@ -27,7 +27,8 @@ fn exec_params_with_argv(process_id: &str, argv: Vec<String>) -> ExecParams {
     ExecParams {
         process_id: ProcessId::from(process_id),
         argv,
-        cwd: PathUri::from_path(std::env::current_dir().expect("cwd")).expect("cwd URI"),
+        cwd: PathUri::from_host_native_path(std::env::current_dir().expect("cwd"))
+            .expect("cwd URI"),
         env_policy: None,
         env: inherited_path_env(),
         tty: false,

codex-rs/exec-server/src/server/processor.rs

@@ -432,7 +432,8 @@ mod tests {
         ExecParams {
             process_id,
             argv: sleep_then_print_argv(),
-            cwd: PathUri::from_path(std::env::current_dir().expect("cwd")).expect("cwd URI"),
+            cwd: PathUri::from_host_native_path(std::env::current_dir().expect("cwd"))
+                .expect("cwd URI"),
             env_policy: None,
             env,
             tty: false,