Exercise resultFromGeminiStream against current stream-json fixtures
(including empty-success hardening). Recognize GEMINI_API_KEY and map
IneligibleTierError to auth — personal OAuth free-tier is no longer
supported by gemini CLI.
Co-authored-by: Cursor <cursoragent@cursor.com>
GeminiAdapter was reading message.text and result.usage, so current CLI
content/stats events produced empty $0 success rows. Accept content with
an assistant role guard, stats token fallbacks, init model, and treat
empty exit-0 output as an error (#2159).
Co-authored-by: Cursor <cursoragent@cursor.com>