nx_build_plan_test.nx

nx_build_plan_test.nx -- verify multi-process schedule solver. Closed-form invariants: (a) plan_new sane: n=0, capacity correct, printer_free zeroed (b) add_part returns sequential ids; bad inputs return negative (c) set_dep updates child's bitmap; self-dep rejected (d) Independent-parts case (no deps, distinct processes): all start at T=0 in parallel, total = max(each) (e) Sequential dep chain (A->B->C): B starts at A.end, C at B.end (f) Same-process serialization: 2 FDM parts share 1 printer, second starts at first.end (g) Cross-process Christus demo: FDM PLA body (240m) + DIW cement (60m+1440m cure) + FDM metal (30m+2880m sinter) all start at T=0 because distinct processes do not contend; total = max(240, 1500, 2910) = 2910 min ≈ 48.5 hours (h) Cycle detection: A<->B returns NX_BUILD_ERR_CYCLE expect_exit: 0 license_tier: ORIGINAL