[#367] Allow users to create and add custom Logger Appenders

[feelform]

• Use internal LogLevel constants
• Appender copy with functions

[Copilot]

Pull Request Overview

This PR replaces usage of the external loglevel library constants with internal LogLevel constants in the logging system. The change centralizes log level management by introducing a new LogLevel class with static getters that define the same numeric values as the external library.

Key changes:

• Introduces a new LogLevel class with static getters for all log levels (TRACE, DEBUG, INFO, WARN, ERROR, SILENT)
• Updates all files to use the internal LogLevel constants instead of loglevel.levels
• Re-enables previously skipped tests in the logger test suite

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
lib/utils/log/log-builder.js	Adds LogLevel class definition and updates all level references to use internal constants
lib/utils/log/logger.js	Replaces loglevel.levels references with internal LogLevel constants
lib/utils/log/index.js	Updates exports to use the new LogLevel class
lib/agent-builder.js	Renames log import to logger for consistency
test/utils/log/logger.test.js	Updates test imports and re-enables skipped tests

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