regalloc.nx

regalloc.nx -- alias stub. The original regalloc.nx was renamed to nx_regalloc.nx in commit 8302d014 (Poletto-Sarkar spillAtInterval eviction). Some consumers were updated (regalloc_test.nx) but others were not (nxc.nx, main.nx, smoke_nxc_pipeline*, etc.). This stub keeps the older import path resolvable so the bootstrap chain stays intact. Mechanism: NishiLang import resolution splices file text inline + dedupes by canonicalised path (see import.nx invariants I1/I3). So `import "regalloc.nx"` -> reads this file -> sees the next line -> reads nx_regalloc.nx -> splices its content. Consumers see every symbol nx_regalloc.nx exports, transparently. This is the four-pillar REPAIR + the S-class movability affordance for the "rename without consumer update" bug class. Pair with bench/nx_import_closure.sh (PREVENT layer) so future moves either leave stubs or fail the audit. Deprecation: when every consumer of "regalloc.nx" has been updated to "nx_regalloc.nx", delete this stub. The closure check will catch any straggler.