Report each failed input check once, and let ComfyUI check the rest

A VALIDATE_INPUTS that takes **kwargs makes ComfyUI skip its own range
and list checks for every input, and a failed check comes back once per
input: Image Crop + Rotate + Pad without a picture showed 20 copies of
"Select or upload a source file first". Each validator now names only
what it reads.

- Image Crop + Rotate + Pad, Load Video and LaMa Inpaint read one input
  and report one error, on it. Video Crop + Rotate + Pad (Frame and
  Clip) read the three that choose the source. LoRA Loader reads the
  stack and on_missing; Save Image reads its two names and output_dir.
- Save Video has no validator any more: ComfyUI's own check holds a
  typed fps to 0.01-240.
- Load Video and the Clip node check the trim window, force_rate and
  Fixed frames as they run, where a wired bound has its value. They are
  async, so ComfyUI starts them ahead of other nodes.
- The sources still skip ComfyUI's list check on purpose, so uploads,
  subfolders, MaskEditor saves and a stale video choice in local path
  mode keep working. The path checks behind them are unchanged.
- crop_aspect_ratio accepts any whole-number W:H, as the transform
  always has, so a workflow made with someone else's presets still runs;
  anything else is now refused before the run.

tests/test_validate_inputs.py pins what each validator names (runs in
CI) and, with ComfyUI, drives ComfyUI's own validation.

docs/adding_a_node.md

@@ -26,6 +26,7 @@ Every visible field and output must earn its place. Published IDs, input order,
 6. Chain lifecycle hooks through `chainCallback`; never replace core or third-party prototypes directly.
 7. Keep normal workflow and API execution independent from the custom frontend.
 8. Ship user-facing toggles as ComfyUI settings under the `AusBoss.*` namespace. Node coloring is automatic for `AUSBOSS_NODES_*` classes via `js/appearance/` — no per-node work.
+9. A `VALIDATE_INPUTS` names only the inputs it reads, never `**kwargs`. ComfyUI skips its own range and list checks for every input a validator names (naming `input_types` also switches off its link checks), and repeats a failed check once per named input. Checks that need several values can run in the node itself. `tests/test_validate_inputs.py` pins what each validator names.
 
 ## Document and prove