继续按 align-linuxcnc 约束：补 word reader 源码错误覆盖

结论：覆盖 LinuxCNC interp_read.cc 中负数 F/G/H/L/M/S/T 和重复 F/H/L/S/T/X/Y/Z word reader 错误；未扩展 smoke。

验证：./test-linuxcnc-source-link.sh；./test-native.sh。

docs/linuxcnc-porting.md

@@ -213,5 +213,6 @@ This matrix tracks LinuxCNC feature coverage for the web/WASM simulator. A featu
 | Probe moves `G38.2/G38.3/G38.4/G38.5` | covered as distinct probe events with LinuxCNC `probe_type` preserved through smoke, native, and source-linked paths | `tests/gcode/linuxcnc_probe_no_error.ngc` |
 | O-word subroutines, calls, and control flow | covered for numeric and named `O... sub/call/return/endsub` plus `if`/`elseif`/`else`, `while`, `repeat`, `do`/`while`, `break`, and `continue` through LinuxCNC file mode; smoke parser also covers named `O<name>` sub/call/return/endsub and loop-control forms | `tests/gcode/smoke_oword_subprogram.ngc`, `tests/gcode/linuxcnc_named_oword_subprogram.ngc`, `tests/gcode/linuxcnc_oword_control_flow.ngc` |
 | Parameter expressions and operators | covered for parameter references, source-linked `mod`, `**`, logical, and relational operator precedence, plus LinuxCNC divide-by-zero, negative-power, malformed `ATAN[]/[]`, unary operation, `read_operation()` binary-operation prefix, unknown operation, and unclosed-expression error paths from `interp_read.cc`/`interp_execute.cc` | `tests/gcode/linuxcnc_parameter_expression_assignment.ngc`, `tests/gcode/linuxcnc_expression_operators.ngc`, `tests/gcode/linuxcnc_divide_by_zero_error.ngc`, `tests/gcode/linuxcnc_negative_power_error.ngc`, `tests/gcode/linuxcnc_atan_missing_slash_error.ngc`, `tests/gcode/linuxcnc_atan_missing_bracket_error.ngc`, `tests/gcode/linuxcnc_unary_missing_bracket_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_word_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_a_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_e_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_g_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_l_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_m_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_n_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_o_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_x_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_operation_error.ngc`, `tests/gcode/linuxcnc_unclosed_expression_error.ngc` |
+| Word reader validation | source-linked LinuxCNC reader errors covered for negative `F/G/H/L/M/S/T` values and repeated `F/H/L/S/T/X/Y/Z` words from `interp_read.cc` | `tests/gcode/linuxcnc_negative_f_word_error.ngc`, `tests/gcode/linuxcnc_negative_g_code_error.ngc`, `tests/gcode/linuxcnc_negative_h_word_error.ngc`, `tests/gcode/linuxcnc_negative_l_word_error.ngc`, `tests/gcode/linuxcnc_negative_m_code_error.ngc`, `tests/gcode/linuxcnc_negative_s_word_error.ngc`, `tests/gcode/linuxcnc_negative_t_word_error.ngc`, `tests/gcode/linuxcnc_multiple_f_words_error.ngc`, `tests/gcode/linuxcnc_multiple_h_words_error.ngc`, `tests/gcode/linuxcnc_multiple_l_words_error.ngc`, `tests/gcode/linuxcnc_multiple_s_words_error.ngc`, `tests/gcode/linuxcnc_multiple_t_words_error.ngc`, `tests/gcode/linuxcnc_multiple_x_words_error.ngc`, `tests/gcode/linuxcnc_multiple_y_words_error.ngc`, `tests/gcode/linuxcnc_multiple_z_words_error.ngc` |
 | Broader canned cycles `G73`, `G74`, `G82`-`G89` | partially covered: `G73`, `G74`, `G82`, `G83`, `G84`, `G85`, `G86`, `G87`, `G88`, `G89`; smoke parser maps supported cycles across `G17/G18/G19`, including LinuxCNC's special non-XY `G74/G84` tapping argument order and `G87` plane-specific `I/J/K` mapping; native/source regressions now check non-XY `G74/G84/G86/G87/G88` sequences | `tests/gcode/linuxcnc_canned_cycles_extended.ngc`, `tests/gcode/linuxcnc_canned_cycle_planes.ngc`, smoke API regression |
 | Full source-level wasm build | covered for the current wasm-safe RS274 source set, with remaining work focused on broadening browser-hostile dependency replacement and feature coverage | `./build-wasm.sh`, `test-linuxcnc-wasm-runtime-link.sh`, `test-web-wasm-node-smoke.sh`, `test-web-wasm-browser-smoke.sh` |