bf94fb2b07
TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 0. Updates the sub-track 4 row from 'ready to start' to 'active 2026-06-19'. Anti-sliming protocol (13 phases, per-site audit, per-phase invariant test) is in effect for the migration of 42 sites in src/gui_2.py.