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/app-server-protocol/schema/json/ServerNotification.json

@@ -3972,7 +3972,7 @@
             "cwd": {
               "allOf": [
                 {
-                  "$ref": "#/definitions/AbsolutePathBuf"
+                  "$ref": "#/definitions/LegacyAppPathString"
                 }
               ],
               "description": "The command's working directory."