fn collect_unique_lines(dir: &Path) -> Result<Vec<String>>Expand description
Collects all JSON lines from every .json file in dir, returning only
the unique ones (deduplicated by primary span + message text).
Only diagnostic messages (compiler-message with spans) are included. Non-diagnostic JSON (build artifacts, build-finished, etc.) is filtered out.
ยงErrors
Returns an error if the directory cannot be read or any file cannot be opened.