Gemini CLI 0.55.0-preview.1: error classification and conversation-state fixes

Preview release bundling the 0.55.0 nightly fixes plus error-handling changes: capacity exhaustion is now terminal rather than retried, and empty-response stream errors surface detail to the UI. Affects anyone testing the preview channel.

Tool: gemini-cli · Version: v0.55.0-preview.1 · Significance: 2/5 · fix