bug: preserve invocation-owned log handlers across nested runs

[codeforester]

Problem

Nested calls to run_app() for the same CLI identity silently remove the outer invocation's logging handlers. ContextVars restore the outer Context, but configure_logger() and cleanup() operate on one process-global logger keyed only by CLI name.

Verified evidence

Reviewed on 2026-09-12 at 7faf347a5b90969e169c88f3ac18e7202d142dd0; the local checkout matches GitHub main.

Create an App named nested with default persistent logging and a boolean --inner option. Its outer callback logs before, invokes run_app(app, ["--inner", "--quiet"]), then logs after; the inner callback logs inner.

Observed: both calls return 0; outer primary.log contains before but no after; inner primary.log contains inner. The inner logger setup closes the outer handlers, and inner cleanup removes its replacements. No application logging exception is raised.

Sources:

• lib/python/base_cli/logging.py
• lib/python/base_cli/context.py
• lib/python/base_cli/_app_core.py

Acceptance criteria

• Either support nested same-identity runs with invocation-owned handlers/restoration or reject unsupported reentrancy before altering the outer run.
• Document the in-process nesting/concurrency boundary.
• Add regressions proving outer logs survive inner success and failure and handlers are closed exactly once.
• Preserve existing multi-process logging behavior.

Project fields

• Status: Backlog
• Priority: P2
• Area: Runtime
• Initiative: v1.0 Readiness
• Size: M
• Assignee: @codeforester
• Milestone: v1.0.0
• Target date: unscheduled