* fix: validate Gemini thinkingLevel against model capabilities and handle empty streams
getGeminiReasoning() now validates the selected effort against the model's
supportsReasoningEffort array before sending it as thinkingLevel. When a
stale settings value (e.g. 'medium' from a different model) is not in the
supported set, it falls back to the model's default reasoningEffort.
GeminiHandler.createMessage() now tracks whether any text content was
yielded during streaming and handles NoOutputGeneratedError gracefully
instead of surfacing the cryptic 'No output generated' error.
* fix: guard thinkingLevel fallback against 'none' effort and add i18n TODO
The array validation fallback in getGeminiReasoning() now only triggers
when the selected effort IS a valid Gemini thinking level but not in
the model's supported set. Values like 'none' (explicit no-reasoning
signal) are no longer overridden by the model default.
Also adds a TODO for moving the empty-stream message to i18n.
* fix: track tool_call_start in hasContent to avoid false empty-stream warning
Tool-only responses (no text) are valid content. Without this,
agentic tool-call responses would incorrectly trigger the empty
response warning message.
a11be8b72e