Use appropriate log levels

Choose log levels based on the intended audience to prevent user-visible noise. Most logging should use Logs.debug rather than Logs.info or Logs.err, since info-level and above messages are visible to end users with --verbose or by default.

Guidelines:

• Use Logs.debug for development/troubleshooting information (parser errors, internal state, performance details)
• Use Logs.info only for information that end users should see with --verbose
• Use Logs.err only for errors that end users need to act upon
• Tagged messages (with ~tags) should generally be debug-level unless specifically intended for users

Example:

(* Bad - creates noise for users *)
Logs.err (fun m -> m ~tags "BUG PARSING LOCAL DECL PROBABLY");
Logs.info (fun m -> m "skipping: %s" (Tok.content_of_tok tok));

(* Good - appropriate for debugging *)  
Logs.debug (fun m -> m ~tags "BUG PARSING LOCAL DECL PROBABLY");
Logs.debug (fun m -> m "skipping: %s" (Tok.content_of_tok tok));

The principle is that no log message should appear to command-line users unless they explicitly enable debugging or the message requires user action.