A seed of -1 means random, as it does everywhere else

Omitting the seed was already random. Passing -1 was not: it went through the
uint64 wrap and arrived as 18446744073709551615, which is a perfectly valid
*fixed* seed -- so "give me something new" returned the identical picture every
time, silently, and the retry loop would have redrawn the same rejected image
until it ran out of attempts.

-1 is what ComfyUI's own interface uses for random, and A1111, and everything
else that has ever asked somebody for a seed. A model that has read any of them
will write it, so the one reading that had to work was the one that did not.

Any negative value, not only -1, because the sentinel is the *idea* rather than
the number and a model that writes -2 means the same thing. Zero stays a real
seed: it is the boundary this change could easily have swallowed, and it is one
somebody deliberately picks.

Confirmed against the real ComfyUI: -1 now sends a random uint64 that it accepts
and draws from.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/lembas/services/images/tool.py

@@ -75,7 +75,10 @@ SCHEMA: dict[str, Any] = {
         },
         "seed": {
             "type": "integer",
-            "description": "Omit for a new random image; repeat one to get the same image again.",
+            "description": (
+                "Omit it, or pass -1, for a new random image. Repeat a seed you were "
+                "told about to get the same image again."
+            ),
         },
         "steps": {"type": "integer", "description": "Sampling steps. Default 20."},
         "cfg": {"type": "number", "description": "Prompt adherence. Default 8."},