Refactor: Remove unused TUI logging mode

[teemow]

Summary

This PR simplifies the logging system by removing the dual-mode (CLI/TUI) architecture that was no longer in use.

Changes

• Remove LogEntry struct, TUI channel, and mode switching logic from pkg/logging
• Simplify InitForCLI to directly set up the slog handler
• Remove Initcommon function and TUI-related code paths
• Update documentation in pkg/logging/doc.go and internal/app/doc.go to reflect CLI-only logging
• Remove dead logToStderr function that was never called
• Fix broken GoDoc list formatting in internal/app/doc.go
• Remove outdated TUI golden files reference from PR template

Benefits

• KISS: Removes ~200 lines of unused dual-mode complexity
• Cleaner API: Single initialization path via InitForCLI
• Better maintainability: No more TUI vs CLI branching in logInternal

Files Changed

File	Change
pkg/logging/logging.go	Remove TUI mode, simplify to CLI-only
pkg/logging/logging_test.go	Remove TUI-related tests
pkg/logging/doc.go	Update documentation for CLI-only mode
internal/app/bootstrap.go	Update comments
internal/app/bootstrap_test.go	Update test names
internal/app/config.go	Remove TUI references in comments
internal/app/doc.go	Update docs, fix list formatting
.github/pull_request_template.md	Remove outdated TUI golden files reference

Test plan

• Unit tests pass (go test ./pkg/logging/... ./internal/app/...)
• No breaking changes (removed types/functions were not used externally)
• CI passes