nx_tool_run_gate.nx

nx_tool_run_gate.nx -- GATE for R0 of the executable-API rung (nx_tool_run). Proves the sovereign exec+capture primitive forks a child, runs a REAL ELF, captures its true stdout, and returns its true exit code -- with a never-brick negative control (a bad path can only yield exit 127 + empty capture, never a shell injection or a persistent-state write). Target = the canonical no-op nx_tool_ping (a SEPARATE tiny ELF, so there is zero recursion risk). Mirrors the nx_*_gate idiom (pass/tot -> GREEN/RED). PREREQ: build nx_tool_ping FIRST (produces _offc/nx_tool_ping.elf). license_tier: ORIGINAL expect_exit: 0