Audit inefficiencies: remove unnecessary jumps and dead assignments

Future optimization: Review all code to identify and remove obvious inefficiencies, such as:\n\n- Unnecessary gotos/gosubs/returns (redundant jumps, double-jumps)\n- Assignments to variables never read (and not kernel/hardware registers)\n- Redundant recomputation of the same value within tight loops\n- Dead labels never targeted\n- No-op sequences (e.g., set X then immediately overwrite)\n- Inefficient multi-branch sequences that can short-circuit earlier\n\nScope:\n- All BASIC routines and inline assembly stanzas\n- Exclude writes that affect TIA/RIOT/kernel state even if never read in BASIC\n\nDeliverables:\n1) A checklist of findings per file\n2) Edits to remove/short-circuit inefficiencies\n3) Notes where behavior must be preserved for timing/kernel interaction\n\nPriority: Future enhancement after core build issues are resolved.