Large files buffered entirely in RAM can OOM workers. Add
max_file_size to source config (default None = no limit).
FS checks stat().st_size before read_bytes(). HTTP and WebDAV issue
a HEAD request before GET when a limit is configured. S3 checks the
size from the existing head_async() call before get_async().
FileTooLargeError is classified as PermanentError so oversized files
go straight to the DLQ instead of retrying.
The previous test deleted a file mid-iteration, but is_file()
caught it before stat() ran — so the new try/except never executed.
Monkeypatch Path.stat to raise FileNotFoundError on the third call
for the victim path (after is_symlink and is_file pass), simulating
the exact TOCTOU window between is_file() and stat().
A file deleted between os.walk() and path.stat() raises
FileNotFoundError, which propagated uncaught and failed the entire
discover() sweep. With enough failures this trips the circuit
breaker, silencing the poller.
Catch FileNotFoundError around the stat() call and skip the file.
The next sweep (or watchfiles) will emit the DELETE event.
