* fix: --config flag now fully overrides ~/.strix/cli-config.json (fixes#377)
Previously, env vars applied from the default config at module import time
were not cleared when --config was later processed, causing settings from
~/.strix/cli-config.json to leak into runs that specified a custom config.
Track which vars were applied by the initial default-config load in
Config._applied_from_default. In apply_config_override, clear those vars
before applying the custom config so only the custom file's settings take effect.
* Add config override regression test
* Make config override test setup explicit
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Co-authored-by: octo-patch <octo-patch@github.com>
Co-authored-by: bearsyankees <bearsyankees@gmail.com>
Octopus