fix(fs): report read errors of readTextFileLines (#3625)

* fix(fs): report read errors of readTextFileLines

In plugins/fs/src/commands.rs read_text_file_lines_next, a read error was
mapped to "not done, empty line", so a persistent error such as EISDIR
(File::open of a directory succeeds on Unix) made the iterator yield ""
forever and the error was swallowed.

The command now closes the resource and returns the error; the JS iterator
resets its rid so a new iteration starts over. api-iife.js regenerated. E2E
spec iterates a directory and expects a rejection.

* fix(fs): close the file when a readTextFileLines loop exits early

In plugins/fs/guest-js/index.ts readTextFileLines, the async iterator did
not implement return(), so breaking out of a for await loop left the
StdLinesResource (an open file) in the webview resource table.

return() now closes the resource and resets the iterator. api-iife.js
regenerated. E2E spec breaks out of a loop, checks the resource id is no
longer valid and that iterating again starts over.

plugins/fs/src/commands.rs

@@ -703,7 +703,12 @@ pub async fn read_text_file_lines_next<R: Runtime>(
                 bytes.push(false as u8);
                 Ok(bytes)
             }
-            Some(Err(_)) => Ok(vec![false as u8]),
+            Some(Err(e)) => {
+                // the error may be persistent (e.g. reading a directory), do not report
+                // an empty line and let the caller loop forever
+                resource_table.close(rid)?;
+                Err(format!("failed to read line with error: {e}").into())
+            }
             None => {
                 resource_table.close(rid)?;
                 Ok(vec![true as u8])