[AJ0070]

The task local storage key (INLINE_LINSOLVE_CACHE, typeof(A), size(A)) got boxed on every lookup, one 48 B allocation per inline linear SCC solve. The caches now sit in one typed Dict under the Symbol key, so the lookup doesn't allocate. Building a missing cache is moved out of line, since inlined it costs every solve ~25 ns on Julia 1.13 and eats the gain.

One allocation less per solve, also under ForwardDiff: the allocation test's RHS call goes from 128 to 80 B (112 to 64 B on 1.10). The lookup takes 19 ns instead of 39, and a model with three blocks 310 ns instead of 380. The test bound is now 256, which leaves room for #168's result array, and the lookup itself is checked to allocate nothing.