Fix: Improve error handling in readConfig() to distinguish read vs parse errors

Problem

The readConfig() function in src/config.ts had imprecise error handling. All errors were reported as "failed to parse config", even when the actual error was a file system issue (e.g., permission denied, file is a directory, I/O error) that occurred during readFileSync().

This made it difficult for users to diagnose configuration issues - a permission problem would be reported as a parse error, leading to confusion.

Solution

Split the error handling into two distinct stages:

1. File read stage - First, read the file content using readFileSync(). Any errors at this stage (file system issues) are now reported as "failed to read config".
2. JSON parse stage - Then, parse the JSON content. Any errors at this stage are reported as "failed to parse config".

Changes

• src/config.ts: Modified readConfig() to separate file reading from JSON parsing
• Error messages now correctly distinguish between:
  • "Error: failed to read config..." (file system issues)
  • "Error: failed to parse config..." (invalid JSON)

Testing

• All existing tests pass (155 tests)
• The change maintains backward compatibility - the same errors are still caught and reported, just with more accurate messages

Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com