lexCodeLines ran every state (code, line comment, block comment, string) through one loop body with three closures over its locals, and shCodeLines and psCodeLines each inlined their escape, quote and comment readers. The C-family lexer now keeps its partial line on a small lx record and dispatches by state to lexNewline, lexLineComment, lexBlockComment, lexString and lexCode, with lexCommentStart, startsJsx and lexStringStart under lexCode. The shell lexers share pushShellLine, readEscapedPair, readQuotedSpan and readLineComment; shCodeLines looks its readers up in a table and psCodeLines splits into psBlockComment and psToken.
Every reader returns the index of the last character it consumed, so the loops advance exactly as before, and the sentinel for an unlexable edit is still null from the C-family path and a null result from the shell paths. Exports are unchanged. A differential run against the previous version over the unit test strings plus 40k generated inputs, across all nine spec shapes change-profile builds, produced identical lines, normalized signatures and isTrivialEdit verdicts.
