fix(windows): broken PATH propagation, ps usage, and claude binary resolution

- sherpa-runtime-env: use case-insensitive key lookup when modifying PATH
  on plain env objects. On Windows, `{...process.env}` stores PATH as
  `Path` but `applySherpaLoaderEnv` used hardcoded `"PATH"`, creating a
  duplicate key that could shadow the real system PATH in child processes.

- runtime-toolchain: use `wmic` on Windows instead of Unix-only `ps -o`
  to resolve the node executable path from a PID.

- claude-agent: pass `findExecutable("claude")` as
  `pathToClaudeCodeExecutable` so the SDK uses the user's installed
  binary when available. Update spawn hook to only replace bare
  "node"/"bun" with process.execPath, preserving native binary paths.

- desktop/paseo.cmd: use ELECTRON_RUN_AS_NODE with node-entrypoint-runner
  for the Windows CLI wrapper.

packages/desktop/bin/paseo.cmd

@@ -9,5 +9,6 @@ if not exist "%APP_EXECUTABLE%" (
   exit /b 1
 )
 
-set "PASEO_DESKTOP_CLI=1"
-"%APP_EXECUTABLE%" %*
+set "ELECTRON_RUN_AS_NODE=1"
+"%APP_EXECUTABLE%" "%RESOURCES_DIR%\app.asar\dist\daemon\node-entrypoint-runner.js" bare "%RESOURCES_DIR%\app.asar\node_modules\@getpaseo\cli\dist\index.js" %*
+exit /b %errorlevel%