继续按 align-linuxcnc 约束：补螺纹和恒线速校验源码覆盖，测试通过

docs/linuxcnc-porting.md

@@ -198,9 +198,9 @@ This matrix tracks LinuxCNC feature coverage for the web/WASM simulator. A featu
 | RTCP controls `G43.4/G43.5/G49` | covered as simulator-owned control lines | `tests/gcode/linuxcnc_rtcp_controls.ngc` |
 | Kinematics switch `M428/M429/M430` | covered as simulator-owned control lines | `tests/gcode/linuxcnc_rtcp_controls.ngc` |
 | Spindle, coolant, program stops, and current tool number `M3/M4/M5`, `M7/M8/M9`, `M0/M1/M60/M30`, `M61 Q...` | covered through LinuxCNC native/source backends, including source-linked `convert_m()` rejection of out-of-range `M3/M4/M5 $` spindle selectors and negative `M61 Q` | `tests/gcode/linuxcnc_spindle_direction.ngc`, `tests/gcode/linuxcnc_coolant.ngc`, `tests/gcode/linuxcnc_program_stops.ngc`, `tests/gcode/linuxcnc_tool_number.ngc`, `tests/gcode/linuxcnc_m3_spindle_dollar_out_of_range_error.ngc`, `tests/gcode/linuxcnc_m4_spindle_dollar_out_of_range_error.ngc`, `tests/gcode/linuxcnc_m5_spindle_dollar_out_of_range_error.ngc`, `tests/gcode/linuxcnc_m61_negative_q_error.ngc` |
-| Spindle speed mode `G96/G97` | covered with Canon `SET_SPINDLE_MODE` preserved as mode state events, including `G96 D...` max-RPM value | `tests/gcode/linuxcnc_spindle_modes.ngc` |
+| Spindle speed mode `G96/G97` | covered with Canon `SET_SPINDLE_MODE` preserved as mode state events, including `G96 D...` max-RPM value and source-linked `check_other_codes()` rejection of missing `S` with `G96` | `tests/gcode/linuxcnc_spindle_modes.ngc`, `tests/gcode/linuxcnc_g96_missing_s_word_error.ngc` |
 | Spindle orientation `M19 R... P... Q...` | covered with Canon `ORIENT_SPINDLE` and `WAIT_SPINDLE_ORIENT_COMPLETE` preserved as temporary mode state events, including source-linked `check_other_codes()` validation for `P/R` words and `convert_m()` rejection of out-of-range `$` selectors and nonpositive `Q` waits | `tests/gcode/linuxcnc_spindle_orient.ngc`, `tests/gcode/linuxcnc_m19_spindle_dollar_out_of_range_error.ngc`, `tests/gcode/linuxcnc_m19_p_not_integer_error.ngc`, `tests/gcode/linuxcnc_m19_p_out_of_range_error.ngc`, `tests/gcode/linuxcnc_m19_r_out_of_range_error.ngc`, `tests/gcode/linuxcnc_m19_zero_q_error.ngc` |
-| Spindle-synchronized feed and threading `G33/G33.1/G76` | covered through smoke, LinuxCNC native, and source-linked paths with Canon `START_SPEED_FEED_SYNCH`/`STOP_SPEED_FEED_SYNCH` preserved, rigid-tap line numbers normalized, and G76 multi-pass threading smoke-covered | `tests/gcode/linuxcnc_threading_sync.ngc`, `tests/gcode/linuxcnc_threading_cycle.ngc`, smoke API regression |
+| Spindle-synchronized feed and threading `G33/G33.1/G76` | covered through smoke, LinuxCNC native, and source-linked paths with Canon `START_SPEED_FEED_SYNCH`/`STOP_SPEED_FEED_SYNCH` preserved, rigid-tap line numbers normalized, G76 multi-pass threading smoke-covered, and source-linked `check_other_codes()` validation for required/disallowed `K/F/P/I/J` words | `tests/gcode/linuxcnc_threading_sync.ngc`, `tests/gcode/linuxcnc_threading_cycle.ngc`, `tests/gcode/linuxcnc_g33_missing_k_word_error.ngc`, `tests/gcode/linuxcnc_g33_f_word_error.ngc`, `tests/gcode/linuxcnc_g33_1_missing_k_word_error.ngc`, `tests/gcode/linuxcnc_g33_1_f_word_error.ngc`, `tests/gcode/linuxcnc_g76_missing_p_word_error.ngc`, `tests/gcode/linuxcnc_g76_missing_i_word_error.ngc`, `tests/gcode/linuxcnc_g76_missing_j_word_error.ngc`, `tests/gcode/linuxcnc_g76_missing_k_word_error.ngc`, smoke API regression |
 | Lathe diameter/radius mode `G7/G8` | covered through LinuxCNC native/source backends for same-block X scaling, `G76` I/J/K threading geometry interaction, and `#<_lathe_diameter_mode>`/`#<_lathe_radius_mode>` readonly named-parameter state | `tests/gcode/linuxcnc_lathe_diameter_mode.ngc`, `tests/gcode/linuxcnc_lathe_diameter_g76.ngc` |
 | Digital/analog I/O `M62`-`M68` | covered with Canon digital output, analog output, and input wait callbacks preserved as temporary state events, including source-linked `convert_m()` validation for required `P`/`E`, M66 input selection, M66 wait timeout, and analog wait restrictions | `tests/gcode/linuxcnc_io_controls.ngc`, `tests/gcode/linuxcnc_m62_missing_p_word_error.ngc`, `tests/gcode/linuxcnc_m63_missing_p_word_error.ngc`, `tests/gcode/linuxcnc_m64_missing_p_word_error.ngc`, `tests/gcode/linuxcnc_m65_missing_p_word_error.ngc`, `tests/gcode/linuxcnc_m66_missing_input_error.ngc`, `tests/gcode/linuxcnc_m66_both_inputs_error.ngc`, `tests/gcode/linuxcnc_m66_zero_timeout_error.ngc`, `tests/gcode/linuxcnc_m66_analog_wait_error.ngc`, `tests/gcode/linuxcnc_m67_missing_e_word_error.ngc`, `tests/gcode/linuxcnc_m68_missing_e_word_error.ngc` |
 | Override controls `M48`-`M53` | covered with Canon feed override, spindle speed override, adaptive feed, and feed hold callbacks preserved as temporary state events | `tests/gcode/linuxcnc_override_controls.ngc` |