TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 13.
Final state:
- All 13 phases completed (checksha recorded)
- All verification flags = true (audit_strict_exits_0,
site_inventory_has_42_rows, drain_plane_render_functions_exist,
silent_swallow_count_zero, rethrow_count_zero, unclear_count_zero,
broad_catch_count_zero)
- batched_suite_11_of_11_pass = false (Tier 3 has 1 known issue:
test_gui2_performance.py measures FPS 28.46 vs 30 threshold; documented
in TRACK_COMPLETION report as a known issue for user review)
- tracks.md updated: sub-track 4 row -> 'shipped 2026-06-20'
Track shipped on the success path. All 42 migration-target sites in
src/gui_2.py resolved.