Add missing environment variables to docs

stack-info: PR: #957, branch: jansel/stack/199

Author: jansel

docs/api/settings.md

@@ -238,13 +238,18 @@ Built-in values for ``HELION_AUTOTUNER`` include ``"PatternSearch"``, ``"Differe
 |----------------------|---------|-------------|
 | ``TRITON_F32_DEFAULT`` | ``dot_precision`` | Sets default floating-point precision for Triton dot products (``"tf32"``, ``"tf32x3"``, ``"ieee"``). |
 | ``HELION_FORCE_AUTOTUNE`` | ``force_autotune`` | Force the autotuner to run even when explicit configs are provided. |
+| ``HELION_DISALLOW_AUTOTUNING`` | ``check_autotuning_disabled`` | Hard-disable autotuning; kernels must supply explicit configs when this is ``1``. |
 | ``HELION_AUTOTUNE_COMPILE_TIMEOUT`` | ``autotune_compile_timeout`` | Maximum seconds to wait for Triton compilation during autotuning. |
+| ``HELION_AUTOTUNE_PRECOMPILE`` | ``autotune_precompile`` | Select the autotuner precompile mode (``"spawn"``, ``"fork"``, or disable when empty). |
+| ``HELION_AUTOTUNE_PRECOMPILE_JOBS`` | ``autotune_precompile_jobs`` | Cap the number of concurrent Triton precompile subprocesses. |
 | ``HELION_AUTOTUNE_RANDOM_SEED`` | ``autotune_random_seed`` | Seed used for randomized autotuning searches. |
 | ``HELION_AUTOTUNE_MAX_GENERATIONS`` | ``autotune_max_generations`` | Upper bound on generations for Pattern Search and Differential Evolution. |
 | ``HELION_AUTOTUNE_ACCURACY_CHECK`` | ``autotune_accuracy_check`` | Toggle baseline validation for candidate configs. |
 | ``HELION_AUTOTUNE_EFFORT`` | ``autotune_effort`` | Select autotuning preset (``"none"``, ``"quick"``, ``"full"``). |
 | ``HELION_REBENCHMARK_THRESHOLD`` | ``autotune_rebenchmark_threshold`` | Re-run configs whose performance is within a multiplier of the current best. |
 | ``HELION_AUTOTUNE_PROGRESS_BAR`` | ``autotune_progress_bar`` | Enable or disable the progress bar UI during autotuning. |
+| ``HELION_CACHE_DIR`` | ``LocalAutotuneCache`` | Override the on-disk directory used for cached autotuning artifacts. |
+| ``HELION_SKIP_CACHE`` | ``LocalAutotuneCache`` | When set to ``1``, ignore cached autotuning entries and rerun searches. |
 | ``HELION_PRINT_OUTPUT_CODE`` | ``print_output_code`` | Print generated Triton code to stderr for inspection. |
 | ``HELION_ALLOW_WARP_SPECIALIZE`` | ``allow_warp_specialize`` | Permit warp-specialized code generation for ``tl.range``. |
 | ``HELION_DEBUG_DTYPE_ASSERTS`` | ``debug_dtype_asserts`` | Inject dtype assertions after each lowering step. |