Clamp Anthropic temperature to [0.0, 1.0] in _build_anthropic_payload (#1737)

Anthropic's Messages API rejects temperature > 1.0 with HTTP 400, but
_build_anthropic_payload forwarded it verbatim. The shipped "Nietzsche" preset
uses temperature 1.2 and the UI slider allows up to 2.0, so every Claude request
under such a preset hard-broke. Clamp into [0.0, 1.0] in the Anthropic builder
only (OpenAI keeps its wider 0.0-2.0 range). Covers all three Anthropic call
paths, which build through this one function. None is passed through unchanged.

Fixes #1615

Co-authored-by: Ethan <23321960+0xLeathery@users.noreply.github.com>

src/llm_core.py

@@ -512,6 +512,12 @@ def _build_anthropic_payload(model, messages, temperature, max_tokens, stream=Fa
             # Convert multimodal content (image_url → image) for Anthropic
             content = _convert_openai_content_to_anthropic(m["content"])
             chat_messages.append({"role": m["role"], "content": content})
+    # Anthropic only accepts temperature in [0.0, 1.0] and 400s on anything above
+    # 1.0. Clamp here (in the Anthropic builder only) so presets/sliders that use
+    # the wider OpenAI 0.0-2.0 range — e.g. the shipped "Nietzsche" preset at 1.2
+    # — don't hard-break every Claude request. OpenAI's own path is left untouched.
+    if temperature is not None:
+        temperature = max(0.0, min(temperature, 1.0))
     payload = {
         "model": model,
         "messages": chat_messages,