feat: add path field to ParsedCommand::Read variant (#5275)

`ParsedCommand::Read` has a `name` field that attempts to identify the
name of the file being read, but the file may not be in the `cwd` in
which the command is invoked as demonstrated by this existing unit test:


0139f6780c/codex-rs/core/src/parse_command.rs (L250-L260)

As you can see, `tui/Cargo.toml` is the relative path to the file being
read.

This PR introduces a new `path: PathBuf` field to `ParsedCommand::Read`
that attempts to capture this information. When possible, this is an
absolute path, though when relative, it should be resolved against the
`cwd` that will be used to run the command to derive the absolute path.

This should make it easier for clients to provide UI for a "read file"
event that corresponds to the command execution.

codex-rs/protocol/src/parse_command.rs

@@ -1,5 +1,6 @@
 use serde::Deserialize;
 use serde::Serialize;
+use std::path::PathBuf;
 use ts_rs::TS;
 
 #[derive(Debug, Clone, PartialEq, Eq, Deserialize, Serialize, TS)]
@@ -8,6 +9,11 @@ pub enum ParsedCommand {
     Read {
         cmd: String,
         name: String,
+        /// (Best effort) Path to the file being read by the command. When
+        /// possible, this is an absolute path, though when relative, it should
+        /// be resolved against the `cwd`` that will be used to run the command
+        /// to derive the absolute path.
+        path: PathBuf,
     },
     ListFiles {
         cmd: String,