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/codex_app_server_protocol.schemas.json

@@ -2378,7 +2378,7 @@
         "cwd": {
           "anyOf": [
             {
-              "$ref": "#/definitions/v2/AbsolutePathBuf"
+              "$ref": "#/definitions/v2/LegacyAppPathString"
             },
             {
               "type": "null"
@@ -17392,7 +17392,7 @@
               "cwd": {
                 "allOf": [
                   {
-                    "$ref": "#/definitions/v2/AbsolutePathBuf"
+                    "$ref": "#/definitions/v2/LegacyAppPathString"
                   }
                 ],
                 "description": "The command's working directory."