unified-exec: retain PathUri in command events (#28780)

## Why

App-server must report command events containing foreign-platform paths
without changing existing client or rollout path-string formats.

## What changed

- retain `PathUri` through exec command begin/end events
- convert cwd values to `LegacyAppPathString` at the app-server
compatibility boundary
- drop command actions with foreign paths and log them
- serialize rollout-trace cwd values using their inferred native path
representation
- restore Wine coverage for retained Windows cwd values and successful
completion

codex-rs/protocol/src/protocol.rs

@@ -3246,7 +3246,7 @@ pub struct ExecCommandBeginEvent {
     /// The command to be executed.
     pub command: Vec<String>,
     /// The command's working directory if not the default cwd for the agent.
-    pub cwd: AbsolutePathBuf,
+    pub cwd: PathUri,
     pub parsed_cmd: Vec<ParsedCommand>,
     /// Where the command originated. Defaults to Agent for backward compatibility.
     #[serde(default)]
@@ -3272,7 +3272,7 @@ pub struct ExecCommandEndEvent {
     /// The command that was executed.
     pub command: Vec<String>,
     /// The command's working directory if not the default cwd for the agent.
-    pub cwd: AbsolutePathBuf,
+    pub cwd: PathUri,
     pub parsed_cmd: Vec<ParsedCommand>,
     /// Where the command originated. Defaults to Agent for backward compatibility.
     #[serde(default)]