feat(BA-3803): add stdout logging for --headless mode

[devyubin]

resolves #7884 (BA-3803)

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue
• Installer updates including:
  • Fixtures for db schema changes
  • New mandatory config options
• Update of end-to-end CLI integration tests in ai.backend.test
• API server-client counterparts (e.g., manager API -> client SDK)
• Test case(s) to:
  • Demonstrate the difference of before/after
  • Demonstrate the flow of abstract/conceptual models with a concrete implementation
• Documentation
  • Contents in the docs directory
  • docstrings in public interfaces and type annotations

[Copilot]

Pull request overview

This PR adds stdout logging support for the installer's --non-interactive mode. When non-interactive mode is enabled, log messages are written to stdout in addition to the textual UI widget, allowing for better visibility in automated/scripted installations.

Key changes:

• Modified SetupLog widget to accept a non_interactive parameter and conditionally write to stdout
• Updated DevSetup and PackageSetup to pass the non_interactive flag to SetupLog instances
• Added Rich Console integration for formatted stdout output

Reviewed changes

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

File	Description
src/ai/backend/install/widgets.py	Added non_interactive parameter to SetupLog, implemented stdout logging via Rich Console when enabled, overrode write() method to duplicate logs to stdout
src/ai/backend/install/app.py	Updated DevSetup and PackageSetup to pass non_interactive flag to SetupLog instances

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[Copilot]

When handling Exception objects, print_exception() is called without arguments, which prints the currently active exception from sys.exc_info(). However, the Exception object passed to this method may not be the currently active exception. Consider passing the exception object explicitly to print_exception() or using print() with the exception object directly, which would be more consistent with the error message on line 69.

Suggested change

	self._stdout_console.print_exception()
	tb = getattr(content, "__traceback__", None)
	if tb is not None:
	self._stdout_console.print(Traceback.from_exception(type(content), content, tb))
	else:
	# Fallback to the current exception if no traceback is attached
	self._stdout_console.print_exception()

[Copilot]

The bare except clause silently suppresses all exceptions that might occur during stdout writing. While this might be intentional to prevent the logging from crashing the application, it makes debugging difficult when stdout logging fails. Consider at least logging the exception to stderr or using a more specific exception type, or add a comment explaining why exceptions must be suppressed here.