Rule × grid matrix

The matrix below is regenerated from discretizations/ and the fixture trees under tests/conformance/ by tools/render_rule_matrix.py. Drop a new rule or a new grid into the catalog and CI updates this view — no hardcoded cells. Use the matrix to answer two questions:

1. (user) “Does rule X work on grid Y?” — applicable cells are coloured; the number is the floor on observed convergence order baked into the rule’s Layer-B fixture (expected_min_order in discretizations/<family>/<rule>/fixtures/convergence/expected.esm).
2. (contributor) “Where are the holes?” — missing cells flag rule × grid pairs the rule declares it serves but where the canonical or convergence fixture has not landed yet.

Cells legend:

• order (green) — applicable, convergence fixture is running, value is the fixture’s expected_min_order floor.
• canonical (blue) — applicable, cross-binding canonical fixture exists but no convergence fixture yet.
• missing (amber) — applicable, no fixture yet (or fixture is structurally skipped pending an ESS harness extension). Visible dispatch hole.
• n/a (muted) — rule does not declare this grid family in its applies_to block.