v0.13.4 — the composite input anchor: a product grain is a first-class pin

WP-GRAIN-1 (ratified 2026-07-29). An inline reduction's input anchor may now pin a product of levels — avg(revenue @ {store*product*cal.month}) — not just a single level. The engine's reduce_series_to_anchor was already composite-grain-native; this lifts the planner's single-level restriction and adjudicates the pin × output-anchor lattice.

• Law 1 — pin_coarser_than_output (REFUSE, minted): a pin coarser than the output refuses with a pin-specific teaching message + two lawful edits. Its own dimension per OF-1.
• Law 2 — redundant_pin (CLARIFY, minted): two cross-comparable pin levels fix one axis, not two.
• Law 4 — the two-stage-statistic disclosure, generalized: composite pin renders as a braced product; a same-case rider names the fixed axis and the reduced-over axes. Immaterial note ⇒ serve (an explicit pin is the asker's uttered denotation).
• F1 flip: the lawful-but-unfaithful two-stage statistic is now a well-formed ask that serves and agrees with its below-surface IR to float precision.

Wire contract unchanged — contract_version stays "1" (two reason codes added inside the existing vocabulary; the envelope shape is untouched).

Rowed future finding: the composite-input × faced-output corner meets the G4 chain guard and refuses chained_crossing — a named refusal, never a silent number.

Triad: columna 0.13.4 · columna-core 0.13.4 · columna-server 0.8.2 (unchanged — additive core feature, no wire change).