Replace print statements with lightweight logging implementation

[jfsanchez91]

Replace print statements with a lightweight logging implementation.

Here is a simple example how users can customize it and how to iterop with Dart package:logging too

// user package:logging config
hierarchicalLoggingEnabled = true;
Logger.root.level = Level.ALL;
Logger.root.onRecord.listen((record) {
  final time = record.time.toIso8601String();
  final level = record.level.name.padRight(7);
  final loggerName = record.loggerName;
  final message = record.message;
  final error = record.error != null ? ' Error: ${record.error}' : '';
  final stack = record.stackTrace != null ? '\n${record.stackTrace}' : '';

  print('$time [$level] $loggerName: $message$error$stack');
});

// interop with package:logging
mcp_dart.Logger.setHandler((name, level, message) {
  final mappedLevel = switch (level) {
    mcp_dart.LogLevel.debug => Level.FINE,
    mcp_dart.LogLevel.info => Level.INFO,
    mcp_dart.LogLevel.warn => Level.WARNING,
    mcp_dart.LogLevel.error => Level.SEVERE,
  };
  Logger(name).log(mappedLevel, message);
});
Logger('mcp_dart').level = Level.INFO;

[codecov]

Codecov Report

❌ Patch coverage is 32.71028% with 72 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.98%. Comparing base (1f08bd5) to head (95c45be).
⚠️ Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/src/client/stdio.dart	30.76%	18 Missing ⚠️
lib/src/server/sse_server_manager.dart	0.00%	10 Missing ⚠️
lib/src/server/stdio.dart	0.00%	9 Missing ⚠️
lib/src/server/server.dart	0.00%	7 Missing ⚠️
lib/src/server/mcp.dart	0.00%	6 Missing ⚠️
lib/src/server/sse.dart	25.00%	6 Missing ⚠️
lib/src/shared/iostream.dart	53.84%	6 Missing ⚠️
lib/src/client/client.dart	55.55%	4 Missing ⚠️
lib/src/shared/protocol.dart	0.00%	3 Missing ⚠️
lib/src/shared/stdio.dart	40.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
+ Coverage   45.55%   45.98%   +0.43%     
==========================================
  Files          15       16       +1     
  Lines        2880     2903      +23     
==========================================
+ Hits         1312     1335      +23     
  Misses       1568     1568              

Flag	Coverage Δ
unittests	45.98% <32.71%> (+0.43%)	⬆️

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[leehack]

@jfsanchez91 Thanks for the PR, but I'm hesitant to add a dependency for logging since I want to make the library as light as possible. Would you mind rewriting a lightweight logger instead of using an external lib?

[jfsanchez91]

@leehack done, now it provides a lightweight logging impl, that can also interop with package:logging if needed