nx_merge_queue.nx

nx_merge_queue.nx -- the SPECULATIVE FIFO merge queue (the research-proven integration layer that GitHub merge queue / GitLab merge trains / Zuul all use; /deep-research wfb7jkc6h). Upgrades nx_workstream_git: each change is tested against the COMBINED state of base + all changes ahead in FIFO order; disjoint changes all land (parallel throughput), an overlapping change is DROPPED (must rebase + re-enter), and a drop does NOT cascade -- downstream changes are re-tested against the merged tip WITHOUT the dropped change (no false failures). This catches the canonical race (both pass alone, break together) that a shared branch misses. license_tier: ORIGINAL Pairs with nx_workstream_git isolation.