nx_doc_kwscan.nx

nx_doc_kwscan.nx -- DOCTOR reserved-keyword diagnosis (the reserved-kw sub-case of empty-.s, the sibling of the let-reassign fixer). When dah_resolve returns DAH_NOFIX on an EMPTYS class, THIS pinpoints WHY: it finds an identifier that collides with a NishiLang reserved keyword used in a position the grammar requires an identifier (a let/var/const/static/func declared NAME, or a parameter NAME), and reports the keyword + byte offset + a safe suggested rename. READ-ONLY BY CONSTRUCTION: it does NOT auto-rewrite -- a blind keyword rename could clobber a legitimate keyword USE (a real `match {}` statement, a `return`, a `while`), so detection + suggestion is the fail-safe boundary (the human/Doctor applies the rename with scope knowledge). The reserved-keyword set is the AUTHORITATIVE lexer list (runtime/lex.nx keyword_lookup, 22 kw) -- NOT folklore: `type`/`import` are NOT lexer keywords, so they are valid identifiers and are deliberately NOT flagged. license_tier: ORIGINAL