TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 3.
Adds _render_main_interface_result(app) -> Result[bool] helper that wraps
the OUTER render-loop try/except from App._gui_func. App._gui_func becomes
a thin wrapper that calls the helper and drains errors to _last_request_errors.
NOTE: the task spec asked for a try/except around the drain to protect the
render frame; this was removed because bare-Exception except/pass would
introduce new INTERNAL_SILENT_SWALLOW violations (constraint violation: the
new code must NOT introduce new violations). The drain logic is
structurally safe (hasattr check + append) and the helper already protects
the render call internally, so no outer try/except is required.
Audit: BROAD_CATCH count 23 -> 22, COMPLIANT count 14 -> 15. Tests: 2/2 pass.
ed
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