bug: localize internal list cli and app scratch state

[codeforester]

Summary

• localize internal list, CLI, and app scratch variables so public calls cannot overwrite caller state
• return CLI option lookup results through explicit output variables instead of implicit globals
• add caller-collision and namespace-regression coverage across list, CLI, and app paths

Validation

• bats lib/bash/list/tests/lib_list.bats lib/bash/cli/tests/lib_cli.bats lib/bash/app/tests/lib_app.bats tests/namespace-contract.bats (48 tests)
• ./tests/validate.sh (571 tests plus option, property, artifact, benchmark, integration, concurrency, quality, compatibility, release, and example gates)

Impact

• Public API: unchanged; an internal CLI lookup helper now uses explicit output arguments
• Documentation: changelog entry only
• CI: namespace contract now rejects undeclared internal globals created by representative public calls
• Demo: no changes required
• Security: no direct security impact

The remaining dynamically scoped supervisor and trap state in the stdlib and GitHub modules is intentional and covered by their lifecycle tests.

Fixes #338