nx_sched_emit.nx

nx_sched_emit.nx -- PREEMPTIVE SCHEDULER emitter (2-task round-robin), the kernel-up rung that flips census GEN-K-preemptive-smp-scheduler from BEHIND toward PRESENT. Builds on the proven timer-interrupt mechanism (nx_timer_irq_emit). AUTHOR=ORGAN: table-computes a bare-metal rv64 qemu-virt image (zero hand-written machine code). Two tasks loop-emit their own marker ('A' / 'B'). The CLINT timer preempts every TICK; the trap handler is the SCHEDULER -- it ROUND-ROBINS the two tasks with the one-instruction trick csrrw t6, mepc, t6 ; atomically swap the interrupted PC <-> the saved task PC (no task-control-block memory, no load needed: two tasks fit in mepc + one register), re-arms the timer (deadline += TICK -> MTIMECMP), counts ticks, and after K ticks clean-halts via the SiFive finisher. The transcript is interleaved RUNS of A and B -- PROOF the scheduler preempted and switched contexts repeatedly. (Interleaving run-length is timing-determined, so the gate asserts the STRUCTURAL property -- >=N A<->B switches -- not a byte-exact golden; honest for a preemptive phenomenon.) Reuses the proven rv64 mini-encoder. Sovereign, no gcc/.sh. license_tier: ORIGINAL