t7_from_t8

In the Recognition Science forcing spine, T8 asserts that spatial dimension is forced to $D=3$ by linking support, eight-tick compatibility, and uniqueness of an RS-compatible dimension. T7 asserts that the minimal ledger-compatible cycle is the eight-tick octave: eight equals $2^3$, and the eight-tick recovered from dimension three coincides with the canonical eight-tick constant.

This module exposes the public theory-only T-1 through T8 spine and deliberately stops before private operator and measurement layers. Upstream, eight_tick_is_2_cubed is the reflexivity proof that the eight-tick constant equals $2^3$ ("8 = 2^3, so eight-tick forces D = 3"). The bridge theorem t8_to_t7_bridge_holds turns a T8 certificate into the T8-to-T7 bridge fields, including the projection that dimension three yields the canonical eight-tick.

Term-mode structure construction with two field assignments. The first field is discharged by DimensionForcing.eight_tick_is_2_cubed, the definitional equality eight_tick = 2^3. The second field applies t8_to_t7_bridge_holds to the T8 hypothesis and projects dimension_three_eight_tick, which states that EightTickFromDimension 3 equals the canonical eight-tick constant. No further tactics or case analysis.

This is the reverse T8 → T7 arrow on the public forcing spine. Primer landmarks: T7 is the eight-tick octave (period $2^3$); T8 is $D=3$ spatial dimensions. Downstream it feeds complete_forcing_chain_t8, the full public T-1..T8 certificate, and the UnifiedForcingChain packaging physical_forcing_chain. It also appears inside T6_To_T7_RouteEquivalence, which certifies that the direct T6→T7 canonical-period route and the indirect T6→T8→T7 dimension route produce the same T7 surface. Without this lemma the dimension-bridge route to eight-tick would not close.