Prepare base_cli for future package extraction

[codeforester]

Project metadata

• Status: Backlog
• Priority: P3
• Area: Python
• Initiative: Adoption Polish
• Size: M

Context

lib/python/base_cli is the strongest candidate for future shared-code extraction. It is already a documented CLI framework and is consumed broadly across Base, but app.py and the package boundary still include Base-specific path/config/history assumptions.

Scope

• Make the public/private boundary of base_cli clearer without moving it to a separate repository.
• Reduce avoidable coupling in base_cli.app where a narrow extraction-safe helper is obvious.
• Preserve all current command behavior.

Validation

• Focused base_cli tests.
• Existing public command lifecycle tests.
• git diff --check.