Merge debug logger into file logger with text-only output

[Copilot]

Debug loggers created with logger.New() now write to both stderr (with colors/time diffs) and the file logger (text-only). This ensures all debug output is persisted to files for production troubleshooting while maintaining real-time colored output during development.

Changes

• internal/logger/logger.go: Modified Printf() and Print() to call LogDebug() after stderr output
• internal/logger/logger_test.go: Added tests validating dual-output behavior and disabled logger behavior
• Documentation: Updated logger/README.md, AGENTS.md, and .github/workflows/go-logger.md to reflect dual-output semantics

Behavior

var log = logger.New("pkg:file")

// When DEBUG=pkg:* is set:
log.Printf("Processing %d items", 42)
// → stderr: pkg:file Processing 42 items +125ms (with colors)
// → file:   [2026-01-11T18:00:00Z] [DEBUG] [pkg:file] Processing 42 items

The file logger captures all enabled debug logs regardless of terminal availability, while stderr output remains conditional on the DEBUG environment variable pattern matching.

Original prompt

Merge debug logger into file logger (text only), update go log improver prompt.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.