§4 landed — vocab / grammar / prompt / grouper encoding of the conditional rule

Evergreen: sn-boundary-averaged-name-multiplicity · landed 2026-07-10

What shipped

Level	Change	Commit
Vocab (ISN)	`constant_on_flux_surface: true` flag on `safety_factor`, `magnetic_shear`, `magnetic_flux`, `pressure` in `physical_bases.yml` and on the flux-label carriers (`toroidal_flux_radius`, `toroidal_flux_coordinate`, `normalized_toroidal_flux_coordinate`, `normalized_poloidal_flux_coordinate`) in `geometry_carriers.yml`; `flux_surface_reduction: true` on the three reduction operators in `operators.yml`. Membership per the locked `flux-function-base-list` decision (definitional-only).	`b8a2024` (ISN)
Grammar (ISN)	IR-level gate in `grammar/model.py`: a flux-surface reduction (`flux_surface_averaged`, `maximum/minimum_over_flux_surface`) applied to a flagged base fails BOTH `parse_standard_name` and `compose_standard_name` (recurses into binary-operator arguments). 19 unit tests in `tests/grammar/test_flux_surface_reduction_gate.py`; full ISN suite 1665 passed / 2 legacy fixtures updated to surface-varying bases.	`b8a2024` (ISN)
Prompts (imas-codex)	`generate_name_dd.md` separatrix_average path-rule row replaced with the conditional rule (locus always; prefix iff not constant_on_flux_surface; flux-function leaves share ONE name across both subtrees). `generate_name_system.md` averaging-operator bullet gains the no-op guard; `review.md` gains check [I2.8] (both directions: no reduction of a flux function; surface-varying averaged leaves must keep the prefix).	`8d6cb77b` (imas-codex)
Audit (imas-codex)	`audits.find_flux_surface_reduction_violations()` — read-only live-catalog probe wired into the `sn run` startup reconcile block (warns with offender list). Pre-collapse it flags exactly 1 live violation: `flux_surface_averaged_magnetic_shear` (superseded by §3).
Grouper (imas-codex)	`harmonize._FAMILY_REDUCTION_OPERATORS`: the three reduction operator tokens now join docs-harmonization families via the edge `operator` token (kind filter unchanged, so the broad unary_prefix class stays out). `derive_edges`/`parents.py` confirmed correct, untouched.

Results

Gate verified end-to-end: flux_surface_averaged_safety_factor_at_plasma_boundary rejected; flux_surface_averaged_electron_density_at_plasma_boundary round-trips.
ISN pin in imas-codex bumped 515d83c → b8a2024 (extras-preserving uv sync --extra test).
Generalisation: no live maximum/minimum_over_flux_surface names exist; summary/volume_average/* (26 leaves / 27 names) explicitly scoped out — a volume average of a flux function is NOT a no-op.